EX-10.2




 Exhibit 10.2 

Execution Version 

SPONSOR LETTER AGREEMENT 

This SPONSOR LETTER AGREEMENT (this “Agreement”) is entered into as of December 2, 2021, by and among Opal
Fuels LLC, a Delaware limited liability company (the “Company”), ArcLight Clean Transition Corp. II, an exempted company incorporated in the Cayman Islands with limited liability (“ACT”), ArcLight CTC Holdings
II, L.P., a Delaware limited partnership (the “ACT Sponsor”), each of Arno Harris, Audrey Lee, Brian Goncher and Steven Berkenfeld (collectively, the “Insiders”) and, solely for purposes of amending the
Sponsor Letter (as defined below), each of John F. Erhard, Daniel R. Revers, Marco F. Gatti, Christine M. Miller, Kerrick S. Knauth (collectively, the “Officers”). Each of the Company, ACT, the ACT Sponsor and each of the Insiders
are sometimes referred to herein individually as a “Party” and collectively as the “Parties.” Each of the ACT Sponsor and each of the Insiders are sometimes referred to herein individually as
a “Shareholder.” Except as otherwise specified herein, capitalized terms used but not otherwise defined herein shall have the meanings ascribed to them in the Business Combination Agreement (as defined below). 

WHEREAS, concurrently with the execution of this Agreement, ACT, the Company and Opal HoldCo LLC, a Delaware limited liability company
and the record and beneficial owner of a majority of the voting and economic rights of the Company (“Opal HoldCo”), entered into that certain Business Combination Agreement (as amended, supplemented or otherwise modified from time
to time in accordance with its terms, the “Business Combination Agreement”); 
 WHEREAS, the Business
Combination Agreement contemplates that, on the terms and subject to the conditions therein, on the Closing Date, ACT will acquire the equity interests and equity-linked securities of the Company, with ACT becoming the sole managing member of the
Company (collectively, and together with the other transactions contemplated by the Business Combination Agreement and the Ancillary Documents, the “Transactions”); 

WHEREAS, reference is hereby made to the following Contracts (collectively, the “Affected Agreements”): 

(A) that certain Letter Agreement dated March 25, 2021 and delivered by the ACT Sponsor, the Insiders and the Officers to ACT
(the “Sponsor Letter”); 
 (B) that certain Warrant Agreement dated March 25, 2021 between ACT and Continental
Stock Transfer & Trust Company, a New York corporation, as warrant agent (the “Warrant Agent” and, such agreement, the “Warrant Agreement”); and 

(C) that certain Registration and Shareholder Rights Agreement dated March 25, 2021 by and among ACT, the ACT Sponsor and certain other
equityholders named therein; 
 WHEREAS, as of the date hereof, each Shareholder, in its respective capacity as such, is the holder
of record and the “beneficial owner” (within the meaning of Rule 13d-3 under the Exchange Act) of the number of (i) Pre-Closing ACT Class A Shares,
(ii) private placement warrants (the “Warrants”) to purchase an aggregate number of Pre-Closing ACT Class A Shares and/or
(iii) Pre-Closing ACT Class B Shares, in each case, set forth on Exhibit A attached hereto opposite such person’s name on such Exhibit (collectively, with respect to
each Shareholder, the “Subject Securities”); 











 WHEREAS, as part of the Transactions, each of the
Pre-Closing ACT Class B Shares will be converted into one Pre-Closing ACT Class A Share and, subsequently, into one Post-Closing ACT Class A Share; 

WHEREAS, in connection with the Transactions, at the Closing, each of ACT, Opal HoldCo, Ares, Hillman, NextEra, the Company and each of
the Shareholders will enter into the Investor Rights Agreement; 
 WHEREAS, in consideration for the benefits to be received by the
ACT Sponsor and each of the Insiders under the terms of the Business Combination Agreement and as a material inducement to the Company and ACT agreeing to enter into and consummate the transactions contemplated by the Business Combination Agreement,
the ACT Sponsor and each of the Insiders agrees to enter into this Agreement and to be bound by the applicable agreements, covenants and obligations contained in this Agreement; and 

WHEREAS, the Parties acknowledge and agree that the Company and ACT would not have entered into and agreed to consummate the
transactions contemplated by the Business Combination Agreement without each of the Shareholders entering into this Agreement and agreeing to be bound by the applicable agreements, covenants and obligations contained in this Agreement. 

AGREEMENT 
 NOW,
THEREFORE, in consideration of the premises and the mutual promises set forth herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties and, solely for purposes of amending
the Sponsor Letter, the Officers, each intending to be legally bound, hereby agree as follows: 
 1. Sponsor Letter. The Company, ACT,
the ACT Sponsor, each Insider and each Officer hereby agree as follows: 
 (a) The Sponsor Letter acknowledges in Section 3 thereof that
ACT shall not enter into a definitive agreement regarding a Business Combination (as defined therein) without the prior consent of the ACT Sponsor. The Transactions constitute a Business Combination for purposes of the Sponsor Letter and the ACT
Sponsor hereby consents to entry into the Business Combination Agreement. 
 (b) The Sponsor Letter provides in Section 3 thereof for
certain requirements of the ACT Sponsor, the Insiders and the Officers in respect of a Business Combination (in each case, as defined therein), including in respect of voting all Founder Shares and Public Shares (in each case, as defined therein)
beneficially owned by the ACT Sponsor and by the Insiders (the “Shares”), as applicable, in favor of such Business Combinations and forgoing redemption rights in respect thereof. The Transactions constitute a Business Combination
for purposes of the Sponsor Letter and the ACT Sponsor, each Insider and each Officer will comply with its, his or her respective obligations under Section 3 of the Sponsor Letter. In furtherance of such obligations, and without limiting the
prior sentence, each Shareholder agrees, that prior to the Expiration Date (as defined below), at any meeting of ACT’s shareholders or any adjournment or postponement thereof, or in connection with any written consent of ACT’s
shareholders, with respect to the Transactions, such Shareholder shall: 

  
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	 	i.	 appear at such meeting or otherwise cause all Shares to be counted as present thereat for purposes of
calculating a quorum; and 


  

	 	ii.	 from and after the date hereof until the Expiration Date, vote (or cause to be voted) or deliver a written
consent (or cause a written consent to be delivered) covering all of the Shares that such Shareholder shall be entitled to so vote: (A) in favor of adoption and approval of the Business Combination Agreement, the Transactions and any other
proposals recommended by ACT’s board of directors in connection with the Transaction as to which shareholders of ACT are called upon to vote or consent to; (B) against any action or agreement that would reasonably be expected to result in
a breach in any material respect of any covenant, representation or warranty or any other obligation or agreement of ACT or its Affiliates under the Business Combination Agreement or that would reasonably be expected to result in any of the
conditions to ACT’s or any of its Affiliates’ obligations under the Business Combination Agreement not being fulfilled; and (iii) against any ACT Acquisition Proposal, or any agreement, transaction or other matter that is intended to,
or would reasonably be expected to, impede, interfere with, delay, postpone, discourage or materially and adversely affect the consummation of the Transactions. The Shareholders shall not take or commit or agree to take any action inconsistent with
the foregoing. 


 (c) Subject to, and conditioned upon the occurrence and effective as of, the Closing, Section 5 of
the Sponsor Letter shall be amended and restated to provide in its entirety as follows: “[Reserved].” 
 (d) Section 4 of the
Sponsor Letter is hereby amended and restated to provide in its entirety as follows: “[Reserved].” For the avoidance of doubt, if the Business Combination Agreement is terminated in accordance with its terms, then this clause (d) (and the
amendment and restatement contemplated by this clause (d)) shall be of no further force and effect and Section 4 of the Sponsor Letter shall be reinstated and effective from and after such time. 

(e) As used herein, “Expiration Date” means the earliest to occur of (i) the Closing, (ii) such date and time as the
Business Combination Agreement shall be terminated in accordance with its terms, and (iii) upon the mutual written agreement of the Parties. 

2. Earn-Out Shares. 

(a) Subject to, and conditioned upon the occurrence of and effective immediately after the Closing, (i) 5% of the Post-Closing ACT Class A
Shares beneficially owned by the ACT Sponsor immediately following the Closing resulting from the conversion of the Pre-Closing ACT Class B Shares in connection with the Transactions (rounded up to the
nearest whole share) shall be subject to the provisions set forth below in this Section 2 (such shares, the “First  

  
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50% Earn-Out Shares”), (ii) an additional 5% of the Post-Closing ACT Class A Shares beneficially owned by the ACT Sponsor
immediately following the Closing resulting from the conversion of the Pre-Closing ACT Class B Shares in connection with the Transactions (rounded up to the nearest whole share) shall be subject to the
provisions set forth below in this Section 2 (such shares, the “Second 50% Earn-Out Shares” and, together with the First 50% Earn-Out Shares, the “Earn-Out Shares”) and (iii) the remaining 90% of the Post-Closing ACT Class A Shares beneficially owned by the ACT
Sponsor immediately following the Closing resulting from the conversion of the Pre-Closing ACT Class B Shares in connection with the Transactions (rounded down to the nearest whole share) shall not be
subject to the provisions set forth below in this Section 2 (such shares, the “Retained Shares”). 

(b) Subject to, and conditioned upon the occurrence of and effective immediately after the Closing, the
Earn-Out Shares shall be unvested and subject to the restrictions and forfeiture provisions set forth in this Section 2. The Earn-Out Shares
shall vest and be released from the provisions set forth in this Section 2 as follows if, during the 60 months following the Closing (the final day of such period, the
“Earn-Out End Date”): 
  

	 	i.	 (A) the VWAP of the Post-Closing ACT Class A Shares over any 20 Trading Days within any 30
consecutive Trading Day period is greater than or equal to $12.50 per share; or (B) a Sale (as defined below) is consummated in which the Post-Closing ACT Class A Shares are valued at greater than or equal to $12.50 per share, in which the
case of either (A) or (B), the First 50% Earn-Out Shares shall vest upon the close of market on the 20th such Trading Day or as of immediately prior to the closing of such Sale, respectively; and



  

	 	ii.	 (A) the VWAP of the Post-Closing ACT Class A Shares over any 20 Trading Days within any 30
consecutive Trading Day period is greater than or equal to $15.00 per share; or (B) a Sale is consummated in which the Post-Closing ACT Class A Shares are valued at greater than or equal to $15.00 per share, in which the case of either
(A) or (B), such Second 50% Earn-Out Shares shall vest upon the close of market on the 20th such Trading Day or as of immediately prior to the closing of such Sale, respectively; 



(each of the occurrences described in the foregoing clauses (i) and (ii), an “Earn-Out Event”).
Any Earn-Out Shares that have not vested in accordance with this Section 2(b) on or before the Earn-Out End Date will be immediately forfeited
at 11:59 p.m., New York, New York time on the Earn-Out End Date. For purposes of this Agreement, “Sale” means (A) a direct or indirect sale, lease, exchange or other transfer (regardless of the
form of the transaction) in one transaction or a series of related transactions of a majority of ACT’s assets, as determined on a consolidated basis, to a third party or third parties acting as a “group” (as defined in
Section 13(d)(3) of the Exchange Act) or (B) any transaction or series of transactions that results, directly or indirectly, in the shareholders of ACT as of immediately prior to such transactions holding, in the aggregate, less than 50%
of the voting Equity Securities of ACT (or any successor of ACT) immediately after the consummation thereof (excluding, for the avoidance of doubt, any Earn-out Shares), in the case of each of clause
(A) or (B), whether by amalgamation, merger, consolidation, arrangement, tender offer, recapitalization, purchase, issuance, sale or transfer of Equity Securities or assets or otherwise. 

  
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 (c) The ACT Sponsor agrees that it shall not engage in any Transfer (as defined in the
Sponsor Letter) with respect to any Earn-Out Shares until such time as the Earn-Out Shares have vested pursuant to Section 2(b).
Notwithstanding the foregoing or anything to the contrary herein, (i) the ACT Sponsor (and, for the avoidance of doubt, any permitted transferees pursuant to this clause (i)) may transfer all or any of the
Earn-Out Shares to a Permitted Transferee (as defined in the Investor Rights Agreement), provided that the transferee shall, in addition to any requirements in the Investor Rights Agreement, agree in
writing that he, she or it is receiving and holding such Earn-Out Shares subject to the provisions of this Section 2 and (ii) from and after a transfer pursuant to clause
(i) of this sentence, all references to the ACT Sponsor in this Section 2 shall include such transferee and shall collectively mean the ACT Sponsor (to the extent that it then holds
Earn-Out Shares) and each permitted transferee of Earn-Out Shares pursuant to clause (i) of this sentence (in each case, to the extent he, she or it then holds Earn-Out Shares). Each transferee of Earn-Out Shares pursuant to clause (i) of the preceding sentence shall be a third party beneficiary of this
Section 2. 
 (d) As used herein, “Trading Day” means any day on which trading is generally conducted on
Nasdaq or any other exchange on which the Post-Closing ACT Class A Shares are traded on or after the Closing and on or prior to the Earn-Out End Date. The Earn-Out
Shares, the applicable Earn-Out Event (and all references to Post-Closing ACT Class A Shares and each of the foregoing in this Agreement) and the $12.50 and $15.00 per share price referenced in
Section 2(b) shall each be adjusted appropriately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or other distribution of securities convertible into Post-Closing ACT
Class A Shares), reorganization, recapitalization, reclassification, combination, exchange of shares or other like change in respect of the Post-Closing ACT Class A Shares (or any other Equity Securities into which they are adjusted
pursuant to this Section 2(d)) at any time prior to the vesting of the Earn-Out Shares pursuant to this Section 2 so as to provide the holders of the Earn-Out Shares with the same economic effect as contemplated by this Section 2 prior to such event and as so adjusted shall, from and after the date of such event, be the Earn-Out Shares and the Earn-Out Events, as applicable. 
 (e) The
Company shall use reasonable best efforts to remain listed as a public company on, and for the Earn-Out Shares to be tradable over, Nasdaq or any other nationally recognized U.S. stock exchange;
provided, however, the foregoing shall not limit the Company or any of its Affiliates from consummating a Sale or entering into a definitive agreement that contemplates a Sale. Subject to this Section 2, upon
the consummation of a Sale, the Company shall have no further obligations under this Section 2(e). 
 (f) At the
time that the Earn-Out Shares become vested pursuant to this Section 2, the Company shall remove any legends, stock transfer restrictions, stop transfer orders or similar restrictions
with respect to the Earn-Out Shares related to such vesting or this Section 2 (other than, for the avoidance of doubt, those that relate to any applicable and then-existing Lock-Up Period (as defined in the Investor Rights Agreement) with respect to such Earn-Out Shares). 

  
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 (g) For the avoidance of doubt, (i) the ACT Sponsor shall retain all of its rights as a
stockholder of the Company with respect to the Earn-Out Shares owned by it during any period of time that such shares are subject to restriction on transfer or sale hereunder, including the right to vote any
such shares and the right to receive dividends and other distributions with respect to such Earn-Out Shares prior to vesting (provided that dividends and other distributions with respect to Earn-Out Shares that are subject to vesting and are unvested at the time of such dividend or distribution shall be set aside by the Company and shall only be paid to such holders upon the vesting of such Earn-Out Shares (and, if any dividends or other distributions with respect to Earn-Out Shares are set aside and such Earn-Out Shares
are subsequently forfeited pursuant to this Section 2, such set aside dividends or distributions shall become the property of the Company)), (ii) any Earn-Out Shares that vest in
accordance with the terms of this Section 2 shall remain subject to any applicable Lock-Up Period set forth in the Investor Rights Agreement and (iii) notwithstanding the
expiration of any Lock-Up Period with respect to any Earn-Out Shares, such shares shall remain subject to any applicable restrictions set forth this
Section 2. 
 (h) The ACT Sponsor intends to make a protective election under Section 83(b) of the Code with
respect to the Earn-Out Shares. 
 3. Anti-Dilution Adjustment Waiver. Subject to, and
conditioned upon the occurrence of and effective as of immediately prior to the Closing, the ACT Sponsor, which is the holder of at least a majority of the outstanding Pre-Closing ACT Class B Shares as of
the date hereof, hereby waives on behalf of the holders of all Pre-Closing ACT Class B Shares, pursuant to and in compliance with ACT’s Governing Documents, any adjustment to the conversion ratio set
forth therein, and any rights to other anti-dilution protections with respect to the Pre-Closing ACT Class B Shares, that may result from the PIPE Financing and/or the consummation of the Transactions.

 4. ACT Expenses. No later than three Business Days prior to the Closing, ACT shall deliver to the Company a reasonably detailed
calculation of the ACT Expenses, along with reasonably detailed supporting documentation. To the extent such ACT Expenses, in the aggregate, would exceed $26,000,000 as of the Closing Date (including, without limitation, any ACT Expenses to be
incurred, to arise or to accrue as a result of the Closing) (such excess ACT Expenses, the “Excess Act Expenses”), the ACT Sponsor shall pay or cause to be paid to the Company such Excess ACT Expenses either (a) in cash by wire
transfer of immediately available funds, pursuant to written wire instructions provided by the Company no later than two Business Days prior to the Closing, (b) by forfeiting Shares (other than Earn-Out
Shares) beneficially owned by the ACT Sponsor to ACT for cancellation (with each Share valued at $10.00 per share for such purposes) or (c) by a combination of cash or forfeited Shares as provided in clauses (a) and (b). 

5. Other Covenants and Agreements. 

(a) Each Shareholder hereby agrees to be bound by and subject to (i) Sections 5.3(a) (Confidentiality and Access to Information) and 5.4
(Public Announcements) of the Business Combination Agreement to the same extent as such provisions apply to the parties thereto, as if such Shareholder is directly a party thereto, and (ii) Section 5.7 (ACT Exclusive Dealing) of the
Business Combination Agreement to the same extent as such provisions apply to ACT, as if such Shareholder is directly party thereto. 

  
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 (b) If applicable, prior to the Closing, each Shareholder hereby agrees to as promptly as
practicable execute and deliver all additional agreements, documents or instruments, take, or cause to be taken, all actions and provide, or cause to be provided, all additional information or other materials as may be necessary or reasonably
advisable, in each case, as mutually reasonably determined and agreed to by ACT and the Company (such determination and agreement not to be unreasonably withheld, conditioned or delayed by either ACT or the Company), in connection with, or otherwise
in furtherance of, the transactions and the other covenants and agreements contemplated by the Business Combination Agreement or this Agreement (provided, however, that in no event shall any Shareholder be obligated to take, approve or
consent to any action that would result in any adverse economic or other material change to the Business Combination Agreement, this Agreement or any other Ancillary Document to which he, she or it is or will be a party). If applicable, from and
after the Closing, the ACT Sponsor and the Company each hereby agrees to as promptly as practicable execute and deliver execute and deliver all additional agreements, documents or instruments, take, or cause to be taken, all actions and provide, or
cause to be provided, all additional information or other materials as may be reasonably necessary to effectuate the purpose of the covenants and agreements of this Agreement that survive the Closing. Notwithstanding the foregoing, no Shareholder or
the Company shall be required to provide any information that is, based on the advice of outside counsel, subject to legal privilege. 
 (c)
Each Shareholder acknowledges and agrees that ACT and the Company are entering into the Business Combination Agreement in reliance upon such Shareholder entering into this Agreement and agreeing to be bound by, and perform, or otherwise comply with,
as applicable, the applicable agreements, covenants and obligations contained in this Agreement and, but for each Shareholder entering into this Agreement and agreeing to be bound by, and perform, or otherwise comply with, as applicable, the
applicable agreements, covenants and obligations contained in this Agreement, ACT and the Company would not have entered into or agreed to consummate the transactions contemplated by the Business Combination Agreement. 

6. Shareholder Representations and Warranties. Each Shareholder represents and warrants, as of the date hereof, solely with respect to
himself, herself or itself, and not on behalf of any other Shareholder, to the Company and ACT as follows: 
 (a) The Shareholder (if not an
individual) is a corporation, limited liability company or other applicable business entity duly organized or formed, as applicable, validly existing and in good standing (or the equivalent thereof, if applicable, in each case, with respect to the
jurisdictions that recognize the concept of good standing or any equivalent thereof) under the Laws of its jurisdiction of formation or organization (as applicable). 

(b) The Shareholder (if not an individual) has the requisite corporate, limited liability company or other similar power and authority and, if
the Shareholder is an individual, legal capacity to execute and deliver this Agreement, to perform his, her or its covenants, agreements and obligations hereunder (including, for the avoidance of doubt, those covenants, agreements and obligations
hereunder that relate to the provisions of the Business Combination Agreement), and to consummate the transactions contemplated hereby. The execution and delivery of this Agreement has been duly authorized by all necessary corporate or other action
on the part of the Shareholder. This Agreement has been duly and validly executed and delivered by the 

  
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Shareholder and constitutes a valid, legal and binding agreement of the Shareholder (assuming that this Agreement is duly authorized, executed and delivered by the other parties hereto),
enforceable against the Shareholder in accordance with its terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium or other Laws affecting generally the enforcement of creditors’ rights and subject to general principles
of equity). 
 (c) No consent, approval or authorization of, or designation, declaration or filing with, any Governmental Entity is required
on the part of the Shareholder with respect to the Shareholder’s execution, delivery or performance of his, her or its covenants, agreements or obligations under this Agreement (including, for the avoidance of doubt, those covenants, agreements
and obligations under this Agreement that relate to the provisions of the Business Combination Agreement) or the consummation of the transactions contemplated hereby, except for (i) any filings with the SEC related to his, her or its ownership
of Equity Securities of ACT or the transactions contemplated by the Business Combination Agreement, this Agreement or any other Ancillary Documents to which he, she or it is a party, or (ii) any other consents, approvals, authorizations,
designations, declarations, waivers or filings, the absence of which would not reasonably be expected to adversely affect the ability of the Shareholder to perform, or otherwise comply with, any of his, her or its covenants, agreements or
obligations hereunder in any material respect. 
 (d) None of the execution or delivery of this Agreement by the Shareholder, the performance
by the Shareholder of any of his, her or its covenants, agreements or obligations under this Agreement or the consummation of the transactions contemplated hereby will, directly or indirectly (with or without due notice or lapse of time or
both) (i) if the Shareholder is not an individual, result in any breach of any provision of the Shareholder’s Governing Documents, (ii) result in a violation or breach of, or constitute a default or give rise to any right of
termination, Consent, cancellation, amendment, modification, suspension, revocation or acceleration under, any of the terms, conditions or provisions of any Contract to which the Shareholder is a party, (iii) violate, or constitute a breach
under, any Order or applicable Law to which the Shareholder or any of his, her or its properties or assets are bound or (iv) other than the restrictions contemplated by this Agreement, the Business Combination Agreement or any other Ancillary
Document to which such Shareholder is or will be a party, result in the creation of any Lien upon the Subject Securities (other than as expressly provided under this Agreement), except, in the case of any of clauses (ii)
and (iii) above, as would not reasonably be expected to adversely affect the ability of the Shareholder to perform, or otherwise comply with, any of his, her or its covenants, agreements or obligations hereunder in any material respect.

 (e) The Shareholder is, as of the date hereof, the record and beneficial owner of the Subject Securities as set forth on Exhibit A
hereto. The Shareholder has the sole right to vote (and provide consent in respect of, as applicable) the Subject Securities set forth on Exhibit A hereto as of the date hereof. Except for this Agreement, the Business Combination Agreement,
the other Ancillary Documents to which he, she or it is or will be a party, the Affected Agreements and the Governing Documents of ACT, the Shareholder is not party to or bound by (i) any option, warrant, purchase right or other Contract that
would reasonably be expected (either alone or in connection with one or more events, developments or events (including the satisfaction or waiver of any conditions precedent)) to require the Shareholder to Transfer any of the Subject Securities or
(ii) any voting trust, proxy or other Contract with respect to the voting or Transfer of any of the Subject Securities, in the case of either clause (i) or (ii), that would reasonably be expected to adversely affect the ability of the
Shareholder to perform, or otherwise comply with, any of his, her or its covenants, agreements or obligations hereunder in any material respect. 

  
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 (f) There is no Proceeding pending or, to the Shareholder’s knowledge, threatened
against or involving the Shareholder or any of his, her or its Affiliates that, if adversely decided or resolved, would reasonably be expected to adversely affect the ability of the Shareholder to perform, or otherwise comply with, any of its
covenants, agreements or obligations under this Agreement in any material respect. 
 (g) The Shareholder, on his, her or its own behalf and
on behalf of his, her or its Representatives, acknowledges, represents, warrants and agrees that he, she or it has conducted his, her or its own independent review and analysis of, and, based thereon, has formed an independent judgment concerning,
the business, assets, condition, operations and prospects of, the Company and the Transactions as he, she or it and his, her or its Representatives have deemed necessary to enable him, her or it to make an informed decision with respect to the
execution, delivery and performance of this Agreement and the Transactions. 
 (h) In entering into this Agreement, the Shareholder has
relied solely on his, her or its own investigation and analysis and the representations and warranties expressly set forth herein and no other representations or warranties of ACT, the Company or any other Person, either express or implied, and the
Shareholder, on his, her or its own behalf and on behalf of his, her or its Representatives, acknowledges, represents, warrants and agrees that, except for the representations and warranties expressly set forth in this Agreement, none of ACT, the
Company or any other Person makes or has made any representation or warranty, either express or implied, to the Shareholder in connection with or related to this Agreement, the Business Combination Agreement or the other Ancillary Documents or the
transactions contemplated hereby or thereby. 
 7. Company and ACT Acknowledgement. In entering into this Agreement, the Business
Combination Agreement and the other Ancillary Documents to which it is or will be a party, neither of the Company nor ACT have relied on any representations or warranties of any Shareholder, either express or implied, except for the representations
and warranties of the Shareholders expressly set forth in this Agreement or in such other Ancillary Documents to which such Shareholders is or will be a party and to which ACT or the Company, as applicable, is or will be a party. 

8. Transfer of Subject Securities. From and after the date hereof and until the earlier of (a) the termination of this Agreement in
accordance with its terms and (b) the Closing, each Shareholder agrees not to (i) Transfer (as defined in the Sponsor Letter) any of the Subject Securities, (ii) enter into (A) any option, warrant, purchase right, or other
Contract that would reasonably be expected (either alone or in connection with one or more events, developments or events (including the satisfaction or waiver of any conditions precedent)) to require the Shareholder to Transfer the Subject
Securities or (B) any voting trust, proxy or other Contract with respect to the voting or Transfer of the Subject Securities, or (iii) take any actions in furtherance of any of the matters described in the foregoing clauses (i) or
(ii); provided, that , notwithstanding any other provision of this Agreement to the contrary, each Shareholder shall be permitted to make transfers to its Affiliates and limited partners, or its or their Affiliates, members or limited
partners, 

  
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so long as (x) prior to any such transfer, such Shareholder shall deliver a written notice of such Transfer to the Company and, (y) as a condition to any such transfer, such permitted
transferee shall execute a joinder and acknowledgement reasonably satisfactory to the Company agreeing to be bound by and made a party to this Agreement; provided, further, that, any such transfer shall not relieve, discharge or
otherwise modify the obligations of such Shareholder under this Agreement. 
 9. Termination. This Agreement shall automatically
terminate, without any notice or other action by any Party or Officer, and be void ab initio, upon the termination of the Business Combination Agreement in accordance with its terms. Upon termination of this Agreement as provided in the
immediately preceding sentence, none of the Parties or Officers shall have any further obligations or Liabilities under, or with respect to, this Agreement. Notwithstanding the foregoing or anything to the contrary in this Agreement, (a) the
termination of this Agreement shall not affect any Liability on the part of any Party or Officer for a Willful Breach of any covenant or agreement set forth in this Agreement prior to such termination or Fraud,
(b) Section 6, this Section 8 and the representations and warranties set forth in Sections 5(g) and (h) shall each survive any termination of this Agreement, and
(c) Sections 9 through 17 shall survive any termination of this Agreement. For purposes of this Agreement, (x) “Willful Breach” means a material breach of this Agreement that is a consequence of an act or a
failure to act by the breaching Party or Officer with the knowledge that the taking of such act or such failure to act would, or would reasonably be expected to, constitute or result in a breach of this Agreement and (y) “Fraud”
means an act or omission by a Party, and requires: (i) a false or incorrect representation or warranty expressly made by such Party in this Agreement, (ii) with actual knowledge (as opposed to constructive, imputed or implied knowledge) by
the Party making such representation or warranty that such representation or warranty expressly set forth in this Agreement is false or incorrect, (iii) an intention to deceive another Party, to induce him, her or it to enter into this
Agreement, (iv) another Party, in justifiable or reasonable reliance upon such false or incorrect representation or warranty expressly set forth in this Agreement, entering into this Agreement, and (v) another Party suffering damage by
reason of such reliance. For the avoidance of doubt, “Fraud” does not include any claim for equitable fraud, promissory fraud, unfair dealings fraud or any torts (including a claim for fraud or alleged fraud) based on negligence or
recklessness. 
 10. No Other Capacity. Notwithstanding anything in this Agreement to the contrary, (a) no Shareholder makes any
agreement or understanding herein in any capacity other than in such Shareholder’s capacity as a record holder and beneficial owner of the Subject Securities (i.e., if such Shareholder is an individual, not in such Shareholder’s capacity
as a director, officer or employee of ACT); and (b) nothing herein will be construed to limit or affect any action or inaction by (i) an Insider or (ii) in the case of the ACT Sponsor, any representative of the ACT Sponsor serving as
a member of the board of directors of ACT or as an officer, employee or fiduciary of ACT, in each case, acting in such person’s capacity as a director, officer, employee or fiduciary of ACT (which such actions shall be governed by the Business
Combination Agreement or such other Ancillary Agreements applicable to action or inaction taken in such capacity). 
 11. Notices. All
notices, requests, claims, demands and other communications hereunder shall be in writing and shall be given (and shall be deemed to have been duly given) by delivery in person, by e-mail (having obtained
electronic delivery confirmation thereof (i.e., an electronic record of the sender that the email was sent to the intended recipient thereof without an “error” or similar message that such email was not received by such intended
recipient)), or by registered or certified mail (postage prepaid, return receipt requested) (upon receipt thereof) to the other Parties as follows: 

  
 10 












 If to ACT or the ACT Sponsor, to: 

c/o ArcLight Clean Transition Corp. II 

200 Clarendon Street, 55th Floor 

Boston, MA 02116 
 Attention:
        General Counsel 
 Email:
              christine.miller@arclightclean.com 
 with a copy (which
shall not constitute notice) to: 
 Kirkland & Ellis LLP 

609 Main Street 
 Houston, TX
77002 
 Attn:                 Doug Bacon, P.C. 

                Julian Seiguer, P.C. 

                Jennifer R. Gasser 

E-mail:
            douglas.bacon@kirkland.com 

                julian.seiguer@kirkland.com


                jennifer.gasser@kirkland.com

 If to the Company, to: 

Opal Fuels LLC 
 One North
Lexington Avenue Suite 1450 
 White Plains, NY 10601 

Attn.:                John H. Coghlin, General Counsel 

Email:               jcoghlin@opalfuels.com 

with a copy (which shall not constitute notice) to: 

Sheppard, Mullin, Richter & Hampton LLP 

30 Rockefeller Plaza 
 New York,
New York 10112 
 Attn.:                Andrew M. Felner 

                John H. Booher 

Email:               afelner@sheppardmullin.com 

                jbooher@sheppardmullin.com

 if to an Insider or an Officer, to the address on the Insider’s or Officer’s respective signature page hereto; 

or to such other address as the party to whom notice is given may have previously furnished to the others in writing in the manner set forth above. 

  
 11 












 1. Entire Agreement. This Agreement, the Business Combination Agreement and documents
referred to herein and therein (including the Ancillary Documents) constitute the entire agreement of the Parties and Officers with respect to the subject matter of this Agreement, and supersede all prior agreements and undertakings, both written
and oral, among the Parties and Officers with respect to the subject matter of this Agreement, except as otherwise expressly provided in this Agreement. In the event and to the extent that there shall be a conflict between the provisions of this
Agreement and the provisions of any Affected Agreement, this Agreement shall control with respect to the subject matter thereof. 
 2.
Amendments and Waivers; Assignment. Any provision of this Agreement may be amended or waived if, and only if, such amendment or waiver is in writing and signed by the Shareholders, the Company and ACT. Notwithstanding the foregoing, no
failure or delay by any Party or Officer, as applicable, in exercising any right hereunder shall operate as a waiver thereof nor shall any single or partial exercise thereof preclude any other or further exercise of any other right hereunder.
Subject to Section 2(d), neither this Agreement nor any of the rights, interests or obligations hereunder shall be assignable by a Shareholder or the Company without ACT’s prior written consent (to be withheld or given
in its sole discretion) or by ACT or a Shareholder without the Company’s prior written consent (to be withheld or given in its sole discretion). Any attempted assignment of this Agreement not in accordance with the terms of this
Section 13 shall be null and void ab initio. 
 3. Fees and Expenses. Except, in the case of ACT and
the Company, as otherwise expressly set forth in the Business Combination Agreement, and without limitation to Section 4, all fees and expenses incurred in connection with this Agreement and the transactions contemplated
hereby, including the fees and disbursements of counsel, financial advisors and accountants, shall be paid by the Party incurring such fees or expenses; provided, that, any such reasonable and documented fees and expenses incurred by the
Shareholders in connection with this Agreement and the transactions contemplated hereby on or prior to the Closing shall be deemed to be fees and expenses of ACT or the ACT Sponsor, as applicable. 

4. No Third Party Beneficiaries. Except as set forth in Section 2(d), this Agreement shall be for the sole
benefit of the Parties and their respective successors and permitted assigns and is not intended, nor shall be construed, to give any Person, other than the Parties and their respective successors and permitted assigns, any legal or equitable right,
benefit or remedy of any nature whatsoever by reason this Agreement. Nothing in this Agreement, expressed or implied, is intended to, or shall be deemed to, create a joint venture. 

5. Miscellaneous. Sections 8.5 (Governing Law), 8.7 (Construction; Interpretation), 8.10 (Severability),
8.11 (Counterparts; Electronic Signatures), 8.15 (Waiver of Jury Trial), 8.16 (Submission to Jurisdiction) and 8.17 (Remedies) of the Business Combination Agreement are incorporated herein by reference and shall apply to
this Agreement, mutatis mutandis. 
 6. No Ownership Interest. Nothing contained in this Agreement will be deemed to vest in
the Company, any Company Affiliated Party, or any ACT Affiliated Party any direct or indirect ownership or incidents of ownership of or with respect to the Subject Securities. All rights, ownership and economic benefits of and relating to the
Subject Securities shall remain vested in and belong to each Shareholder, and the Company and ACT (and each other Company Affiliated Party and ACT Affiliated Party) shall have no authority to manage, direct, superintend, restrict, regulate, govern
or administer any of the policies or operations of Company or exercise any power or authority to direct any Shareholder in the voting of any of the Subject Securities, except as otherwise expressly provided herein with respect to the Subject
Securities. Except as otherwise set forth in Section 1, no Shareholder shall be restricted from voting in favor of, against or abstaining with respect to any other matters presented to the stockholders of ACT. 

  
 12 












 7. No Recourse. Except for claims pursuant to the Business Combination Agreement or
any Ancillary Document by any party(ies) thereto against any other party(ies) on the terms and subject to the conditions therein, each Party agrees that (a) this Agreement may only be enforced against, and any action for breach of this
Agreement may only be made against, the Parties, and no claims of any nature whatsoever arising under or relating to this Agreement, the negotiation hereof or its subject matter, or the transactions contemplated hereby shall be asserted against any
Person that is not a Party, and (b) without limiting the generality of the foregoing, no Person that is not a Party shall have any Liability arising out of or relating to this Agreement, the negotiation hereof or its subject matter, or the
transactions contemplated hereby, including with respect to any claim (whether in tort, contract or otherwise) for breach of this Agreement or in respect of any written or oral representations made or alleged to be made in connection herewith,
except as expressly provided herein. Notwithstanding anything to the contrary in this Agreement, (i) in no event shall any Shareholder have any obligations or Liabilities related to or arising out of the covenants, agreements, obligations,
representations or warranties of any other Shareholder under this Agreement (including related to or arising out of the breach of any such covenant, agreement, obligation, representation or warranty by any other Shareholder), and (ii) in no
event shall ACT have any obligations or Liabilities related to or arising out of the covenants, agreements, obligations, representations or warrants of any Shareholder under this Agreement (including related to or arising out of any breach of any
such covenant, agreement, obligation, representation or warranty by any such Shareholder). 
 8.
Non-Survival. The representations, warranties, agreements and covenants in this Agreement shall terminate at the Closing, except for those covenants and agreements in this Agreement that, by their
terms, expressly contemplate performance or survival after the Closing (including, without limitation, Sections 1(c), 2, 3, 4, 5(a), and 9 through and including 19) which covenants and agreements shall so survive the Closing in
accordance with their terms; provided that the foregoing shall not limit any Party’s rights in the event of another Party’s Willful Breach of any agreement and covenant set forth in Section 8 prior to the Closing. 

[Signature pages follow.] 

  
 13 












 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	OPAL FUELS LLC
		
	By:	 	 /s/ Adam Comora

	Name: Adam Comora
	Title: Co-CEO


 [Signature Page to Sponsor Letter Agreement] 











 N WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	ARCLIGHT CLEAN TRANSITION CORP. II
		
	By:	 	 /s/ John F. Erhard

	Name: John F. Erhard
	Title: President and Chief Executive Officer


 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	ARCLIGHT CTC HOLDINGS II, L.P.
	
	By: ACTC HOLDINGS GP II, LLC, its general partner
	
	By: ARCLIGHT CAPITAL HOLDINGS, LLC, its Manager
	By: ACHP II, L.P., its Managing Member
	By: ACH GP, LLC, its General Partner
		
	By:	 	 /s/ Daniel R. Revers

	Name: Daniel R. Revers
	Title: Manager


 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	OFFICERS
	
	 /s/ John F. Erhard

	Name: John F. Erhard
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	OFFICERS
	
	 /s/ Daniel R. Revers

	Name: Daniel R. Revers
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	 OFFICERS

	
	 /s/ Marco F. Gatti

	 Name: Marco F. Gatti

	 Address:
	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	OFFICERS
	
	 /s/ Christine M. Miller

	Name: Christine M. Miller
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	OFFICERS
	
	 /s/ Kerrick S. Knauth

	Name: Kerrick S. Knauth
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	INSIDERS
	
	 /s/ Arno Harris

	Name: Arno Harris
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	INSIDERS
	
	 /s/ Audrey Lee

	Name: Audrey Lee
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	INSIDERS
	
	 /s/ Brian Goncher

	Name: Brian Goncher
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 IN WITNESS WHEREOF, the Parties have executed and delivered this Agreement as of the date
first above written. 
  

			
	INSIDERS
	
	 /s/ Steven Berkenfeld

	Name: Steven Berkenfeld
	Address:	 	  

		 	  



 [Signature Page to Sponsor Letter Agreement] 











 EXHIBIT A 

Subject Securities 











 EXHIBIT A 

Subject Securities 
  

									
	 Shareholders
	  	Pre-Closing ACT Class B
Shares	 	  	Pre-Closing ACT Warrants	 
	 ArcLight CTC Holdings II, L.P.
	  	 	6,920,326	 	  	 	9,223,261	 
	 Arno Harris
	  	 	35,000	 	  	 	—  	 
	 Audrey Lee
	  	 	35,000	 	  	 	—  	 
	 Brian Goncher
	  	 	35,000	 	  	 	—  	 
	 Steven Berkenfeld
	  	 	35,000	 	  	 	—  	 
		  	  
	  
	 	  	  
	  
	 
	 Total
	  	 	7,779,076	 	  	 	9,223,261	 
		  	  
	  
	 	  	  
	  
	 

 [Exhibit A to Sponsor Letter Agreement]