<PAGE>
                                       
                        REGISTRATION RIGHTS AGREEMENT


          This Registration Rights Agreement, dated as of March 6, 1998 (this 
"Agreement"), is entered into by and between Energy BioSystems Corporation, a 
Delaware corporation (the "Company"), and Petro Star Inc., an Alaska 
corporation ("Petro Star").

                             W I T N E S S E T H:

          WHEREAS, the Company issued a Warrant dated March 6, 1998 (the 
"Warrant") to Petro Star entitling Petro Star to purchase 200,000 shares of 
the Common Stock, par value $0.01 per share ("Common Stock"), of the Company; 
and

          WHEREAS, the Company has agreed to grant certain registration 
rights in connection with the issuance of the Warrant;

          NOW, THEREFORE, the parties hereto agree as follows:

          1.   CERTAIN DEFINITIONS.  As used in this Agreement, the 
following terms shall have the meanings set forth below:

          (a)  "COMMERCIALLY REASONABLE EFFORTS," when used with respect to 
an obligation to be performed or term or provision to be observed hereunder, 
shall mean such efforts as a prudent person seeking the benefits of such 
performance or action would make, use, apply or exercise to preserve, protect 
or advance its rights or interests, PROVIDED that such efforts do not require 
such person to incur a material financial cost or a substantial risk of 
material liability unless such cost or liability (i) would customarily be 
incurred in the course of performance or observance of the relevant 
obligation, term, or provision, (ii) is caused by or results from the 
wrongful act or negligence of the person whose performance or observance is 
required hereunder or (iii) is not excessive or unreasonable in view of the 
rights or interests to be preserved, protected or advanced.  Such efforts may 
include, without limitation, (A) the expenditure of such funds and retention 
by such person of such accountants, attorneys or other experts or advisors as 
may be necessary or appropriate to effect the relevant action, (B) the 
undertaking of any special audit or internal investigation that may be 
necessary or appropriate to effect the relevant action and (C) the 
commencement, termination or settlement of any action, suit or proceeding 
involving such person to the extent necessary or appropriate to effect the 
relevant action.

          (b)  "COMMISSION" shall mean the Securities and Exchange Commission or
     any other federal agency at the time administering the Securities Act.

          (c)  "COMPANY" shall have the meaning set forth in the initial
     paragraph of this Agreement.

          (d)  "COMMON STOCK" shall have the meaning set forth in the recitals
     of this Agreement. 

          (e)  "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as
     amended, or any similar successor federal statute and the rules and
     regulations thereunder, all as the same shall be in effect from time to
     time.

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          (f)  "HOLDER" shall mean Petro Star and any holder of Registrable
     Securities to whom the registration rights conferred by this Agreement have
     been transferred in compliance with Section 9 hereof.

          (g)  "INITIATING HOLDERS" shall mean any Holder or Holders who in the
     aggregate hold not less than all of the outstanding Registrable Securities.

          (h)  The terms "REGISTER," "REGISTERED" and "REGISTRATION" shall refer
     to a registration effected by preparing and filing a registration statement
     in compliance with the Securities Act and applicable rules and regulations
     thereunder, and the declaration or ordering of the effectiveness of such
     registration statement.

          (i)  "REGISTRABLE SECURITIES" shall mean (i) the shares of Common
     Stock issued or issuable upon exercise of the Warrant and (ii) any Common
     Stock issued as a dividend or other distribution with respect to or in
     exchange for or in replacement of such shares or other securities,
     PROVIDED, HOWEVER, that Registrable Securities shall not include any shares
     of Common Stock which have previously been registered under the Securities
     Act, which have been sold or otherwise transferred under Rule 144 or which
     may be sold without restriction pursuant to Rule 144(k).

          (j)  "REGISTRATION EXPENSES" shall mean all expenses incurred in
     effecting any registration pursuant to this Agreement, including, without
     limitation, all registration, qualification, and filing fees, printing
     expenses, escrow fees, fees and disbursements of counsel for the Company,
     blue sky fees and expenses, and expenses of any regular or special audits
     incident to or required by any such registration, but shall not include
     Selling Expenses and fees and disbursements of counsel for the Holders (and
     shall not include the compensation of regular employees of the Company,
     which shall be paid in any event by the Company).

          (k)  "RULE 144" shall mean Rule 144 as promulgated by the Commission
     under the Securities Act, as such Rule may be amended from time to time, or
     any similar successor rule that may be promulgated by the Commission.

          (l)  "RULE 145" shall mean Rule 145 as promulgated by the Commission
     under the Securities Act, as such Rule may be amended from time to time, or
     any similar successor rule that may be promulgated by the Commission.

          (m)  "SECURITIES ACT" shall mean the Securities Act of 1933, as
     amended, or any similar successor federal statute and the rules and
     regulations thereunder, all as the same shall be in effect from time to
     time.

          (n)  "SELLING EXPENSES" shall mean all underwriting discounts and
     selling commissions applicable to the sale of Registrable Securities and
     all fees and disbursements of counsel for any Holder (other than the fees
     and disbursements of counsel included in Registration Expenses or paid by
     the Company pursuant to Section 4).

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          2.   DEMAND REGISTRATION.  

          2.1  REQUEST FOR REGISTRATION.  (a) If the Company shall receive 
from Initiating Holders, at any time or times not earlier than the date on 
which the Warrant first becomes exercisable, a written request that the 
Company effect any registration with respect to all of the Registrable 
Securities, the Company will as soon as practicable, use Commercially 
Reasonable Efforts to effect such registration (including, without 
limitation, filing a registration statement and any appropriate pre-effective 
or post-effective amendments, appropriate qualifications under applicable 
blue sky or other state securities laws, and appropriate compliance with the 
Securities Act) so as to permit or facilitate the sale and distribution of 
all of the Registrable Securities as specified in such request.

          (b)  The Company shall not be obligated to effect, or to take any 
action to effect, any such registration pursuant to this Section 2:

          (i)   in any particular jurisdiction in which the Company would be
     required to execute a general consent to service of process in effecting
     such registration, qualification, or compliance, unless the Company is
     already subject to service in such jurisdiction and except as may be
     required by the Securities Act;

          (ii)  prior to the expiration of a period of six months after the
     Company has initiated any previous registration pursuant to this Section
     2.1, or after the Company has initiated a total of three such registrations
     pursuant to this Section 2.1, PROVIDED that a registration initiated
     pursuant to this Section 2.1 and subsequently withdrawn by the Holders
     registering shares therein shall not be counted as a requested registration
     pursuant to this clause (ii) if such withdrawal is based upon material
     adverse information relating to the Company that is not known by the
     Initiating Holders at the time of their request for registration pursuant
     to this Section 2.1 or if the Holders bear the Registration Expenses for
     such registration;

          (iii) during the period starting with the date 60 days prior to
     the Company's good faith estimate of the date of filing of, and ending on a
     date 180 days after the effective date of, a Company-initiated
     registration, PROVIDED that the Company is actively employing in good faith
     all Commercially Reasonable Efforts to cause such registration statement to
     become effective;

          (iv)  if the Initiating Holders do not request that such offering be
     firmly underwritten by underwriters selected by a majority in interest of
     the Initiating Holders (subject to the consent of the Company, which
     consent will not be unreasonably withheld);

          (v)   if the Company and the Initiating Holders are unable to obtain
     the commitment of the underwriters described in clause (iv) above to firmly
     underwrite the offer; or

          (vi)  if, within 14 days after its receipt of a written request to
     effect such registration, the Company causes to be delivered to the
     Initiating Holders an opinion of counsel reasonably acceptable to the
     Initiating Holders to the effect that the proposed disposition of
     Registrable Securities by the Initiating Holders will not require
     registration or qualification under the Securities Act, it being
     specifically understood and agreed that the Initiating Holders will
     promptly furnish to the Company and such counsel all information such
     counsel may reasonably request in order to enable such counsel to determine
     whether it would be able to render such opinion.

                                      -3-
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          2.2  RIGHT TO DEFER REGISTRATION.  Subject to the provisions of 
Section 2.1(b), the Company shall use Commercially Reasonable Efforts to file 
a registration statement covering the Registrable Securities so requested to 
be registered as soon as practicable after receipt of the request or requests 
of the Initiating Holders; PROVIDED, HOWEVER, that if (i) in the good faith 
judgment of the Board of Directors of the Company, such registration would be 
seriously detrimental to the Company and the Board of Directors of the 
Company concludes, as a result, that it is essential to defer the filing of 
such registration statement at such time, and (ii) the Company shall furnish 
to such Holders a certificate signed by the President of the Company stating 
that in the good faith judgment of the Board of Directors of the Company, it 
would be seriously detrimental to the Company for such registration statement 
to be filed in the near future and that it is, therefore, essential to defer 
the filing of such registration statement, then the Company shall have the 
right to defer such filing for the period during which such disclosure would 
be seriously detrimental, PROVIDED that (except as provided in Section 
2.1(b)(iii) above) the Company may not defer the filing for a period of more 
than 90 days after receipt of the request of the Initiating Holders, and, 
PROVIDED FURTHER, that the Company shall not defer its obligation in this 
manner more than once in any twelve-month period.

          2.3  UNDERWRITING.  (a) The right of any Holder to registration 
pursuant to Section 2 shall be conditioned upon such Holder's participation 
in such underwriting and the inclusion of such Holder's Registrable 
Securities in the underwriting to the extent provided herein.  All Holders 
proposing to distribute their securities through such underwriting (together 
with the Company and other holders of securities of the Company exercising 
registration rights with respect to such registration) shall enter into an 
underwriting agreement in customary form with the representative of the 
underwriter or underwriters selected by a majority in interest of the 
Initiating Holders, subject to the consent of the Company, which consent 
shall not be unreasonably withheld.  

          (b)  Notwithstanding any other provision of this Section 2, if the 
representative of the underwriters advises the Initiating Holders in writing 
that marketing factors require a limitation on the number of shares to be 
underwritten, the number of shares to be included in the underwriting or 
registration shall be allocated as set forth in Section 10 hereof.  If a 
person who has requested inclusion in such registration as provided above 
does not agree to the terms of any such underwriting, such person shall be 
excluded therefrom by written notice from the Company, the underwriter or the 
Initiating Holders.  Any Registrable Securities or other securities excluded 
or withdrawn from such underwriting shall also be withdrawn from such 
registration.  If shares are so withdrawn from the registration and if the 
number of shares to be included in such registration was previously reduced 
as a result of marketing factors pursuant to this Section 2.3, then the 
Company shall offer to all Holders who have retained rights to include 
securities in the registration the right to include additional securities in 
the registration in an aggregate amount equal to the number of shares so 
withdrawn, with such shares to be allocated among such Holders requesting 
additional inclusion in accordance with Section 10 hereof. 

          3.   PIGGYBACK REGISTRATION.  

          3.1  NOTICE OF REGISTRATION.  If the Company shall determine to 
register any of its securities either for its own account or the account of a 
security holder or holders exercising their respective demand registration 
rights (other than pursuant to Section 2 hereof), other than a registration 
relating solely to employee benefit plans, a registration relating solely to 
a Rule 145 transaction, or a registration on any registration form that does 
not permit secondary sales, the Company will:

          (i)  promptly give to each Holder written notice thereof; and 

                                      -4-
<PAGE>

          (ii) use Commercially Reasonable Efforts to include in such
     registration (and any related qualification under blue sky laws or other
     compliance), except as set forth in Section 3.2 below, and in any
     underwriting involved therein, all the Registrable Securities specified in
     a written request or requests, made by any Holder within 20 days after the
     written notice from the Company described in clause (i) above is given. 
     Such written request may specify all or a part of a Holder's Registrable
     Securities.

          3.2  RIGHT TO TERMINATE REGISTRATION.  The Company shall have the 
right to terminate or withdraw any registration initiated by it under this 
Section 3 prior to the effectiveness of such registration whether or not any 
Holder has elected to include Registrable Securities in such registration.

          3.3  UNDERWRITING.  (a) If the registration of which the Company 
gives notice is for a registered public offering involving an underwriting, 
the Company shall so advise the Holders as a part of the written notice given 
pursuant to Section 3.1 above.  In such event, the right of any Holder to 
registration pursuant to this Section 3 shall be conditioned upon such 
Holder's participation in such underwriting and the inclusion of such 
Holder's Registrable Securities in the underwriting to the extent provided 
herein.  All Holders proposing to distribute their securities through such 
underwriting (together with the Company and such other holders of securities 
of the Company exercising registration rights with respect to such 
registration) shall enter into an underwriting agreement in customary form 
with the representative of the underwriter or underwriters selected by the 
Company or the security holders initiating such registration, as the case may 
be.

          (b)  Notwithstanding any other provision of this Section 3, if the 
representative of the underwriters advises the Company in writing that 
marketing factors require a limitation on the number of shares to be 
underwritten, the representative may (subject to the limitations set forth 
below) exclude all Registrable Securities from, or limit the number of 
Registrable Securities to be included in, the registration and underwriting.  
The Company shall so advise all holders of securities requesting 
registration, and the amount of securities that are entitled to be included 
in the registration and underwriting shall be allocated first to the Company 
for securities being sold for its own account and thereafter as set forth in 
Section 10 hereof.  If any person does not agree to the terms of any such 
underwriting, such person shall be excluded therefrom by written notice from 
the Company or the underwriter.  Any Registrable Securities or other 
securities excluded or withdrawn from such underwriting shall be withdrawn 
from such registration.

          4.   EXPENSES OF REGISTRATION.  All Registration Expenses incurred 
in connection with any registration, qualification or compliance pursuant to 
Section 3 hereof, and all Registration Expenses and reasonable fees of one 
counsel for the selling stockholders in the case of the first registration 
pursuant to Section 2, shall be borne by the Company.  All Registration 
Expenses and expenses of counsel for the selling stockholders in any 
subsequent registration pursuant to Section 2 shall be borne by the holders 
of the securities so registered pro rata on the basis of the number of shares 
of securities so registered on their behalf.  All Selling Expenses relating 
to securities so registered shall be borne by the holders of such securities 
pro rata on the basis of the number of shares of securities so registered on 
their behalf.

          5.   REGISTRATION PROCEDURES.  In the case of each registration 
effected by the Company pursuant to this Agreement, the Company will keep 
each Holder advised in writing as to the initiation of each registration and 
as to the completion thereof.  At its expense (except, as otherwise provided 
herein), the Company will use Commercially Reasonable Efforts to:

          (a)  keep such registration effective for a period of 120 days or 
     until the Holder or Holders have completed the distribution described in 
     the registration statement relating thereto, 

                                      -5-
<PAGE>

     whichever first occurs; PROVIDED, HOWEVER, that such 120-day period 
     shall be extended for a period of time equal to the period after the 
     effectiveness of such requirements that the Holder refrains from 
     selling any securities included in such registration at the request of 
     an underwriter of Common Stock (or other securities) of the Company;

          (b)  prepare and file with the Commission such amendments and
     supplements to such registration statement and the prospectus used in
     connection with such registration statement as may be necessary to comply
     with the provisions of the Securities Act with respect to the disposition
     of all securities covered by such registration statement;

          (c)  furnish such number of prospectuses and other documents incident
     thereto, including any amendment of or supplement to the prospectus, as a
     Holder from time to time may reasonably request;

          (d)  notify each seller of Registrable Securities covered by such
     registration statement at any time when a prospectus relating thereto is
     required to be delivered under the Securities Act of the happening of any
     event as a result of which the prospectus included in such registration
     statement, as then in effect, includes an untrue statement of a material
     fact or omits to state a material fact required to be stated therein or
     necessary to make the statements therein, in the light of the circumstances
     then existing, not misleading, and at the request of any such seller,
     prepare and furnish to such seller a reasonable number of copies of a
     supplement to or an amendment of such prospectus as may be necessary so
     that, as thereafter delivered to the purchasers of such shares, such
     prospectus shall not include an untrue statement of a material fact or omit
     to state a material fact required to be stated therein or necessary to make
     the statements therein, in the light of the circumstances then existing,
     not misleading;

          (e)  cause all such Registrable Securities registered pursuant
     hereunder to be listed on each securities exchange on which similar
     securities issued by the Company are then listed;

          (f)  provide a transfer agent and registrar for all Registrable
     Securities registered pursuant to such registration statement and a CUSIP
     number for all such Registrable Securities, in each case not later than the
     effective date of such registration; and

          (g)  comply with all applicable rules and regulations of the
     Commission, and make available to its security holders, as soon as
     reasonably practicable, an earnings statement covering the period of at
     least twelve months, but not more than eighteen months, beginning with the
     first month after the effective date of the Registration Statement, which
     earnings statement shall satisfy the provisions of Section 11(a) of the
     Securities Act. 

In connection with any underwritten offering pursuant to a registration
statement filed pursuant to Section 2 hereof, the Company will enter into an
underwriting agreement reasonably necessary to effect the offer and sale of
Common Stock, PROVIDED such underwriting agreement contains customary
underwriting provisions.

          6.   INDEMNIFICATION.  

          (a)  The Company will indemnify each Holder, each of its officers, 
directors and partners, legal counsel, and accountants and each person 
controlling such Holder within the meaning of Section 15 of the Securities 
Act, if Registrable Securities of such Holder are included in the securities 
with respect to which registration, qualification, or compliance has been 
effected pursuant to this Agreement, and 

                                      -6-
<PAGE>

each underwriter, if any, and each person who controls within the meaning of 
Section 15 of the Securities Act any underwriter, against all expenses, 
claims, losses, damages, and liabilities (or actions, proceedings, or 
settlements in respect thereof) arising out of or based on any untrue 
statement (or alleged untrue statement) of a material fact contained in any 
prospectus, offering circular, or other document (including any related 
registration statement, notification, or the like) incident to any such 
registration, qualification, or compliance, or based on any omission (or 
alleged omission) to state therein a material fact required to be stated 
therein or necessary to make the statements therein not misleading, or any 
violation by the Company of the Securities Act or any rule or regulation 
thereunder applicable to the Company and relating to action or inaction 
required by the Company in connection with any such registration, 
qualification, or compliance, and will reimburse each such Holder, each of 
its officers, directors, partners, legal counsel, and accountants and each 
person controlling such Holder, each such underwriter, and each person who 
controls any such underwriter, for any legal and any other expenses 
reasonably incurred in connection with investigating and defending or 
settling any such claim, loss, damage, liability, or action, PROVIDED that 
the Company will not be liable in any such case to the extent that any such 
claim, loss, damage, liability, or expense arises out of or is based on any 
untrue statement or omission based upon written information furnished to the 
Company by such Holder or underwriter and stated to be specifically for use 
therein.  It is agreed that the indemnity agreement contained in this Section 
6(a) shall not apply to amounts paid in settlement of any such loss, claim, 
damage, liability, or action if such settlement is effected without the 
consent of the Company (which consent has not been unreasonably withheld).

          (b)  Each Holder (an "Indemnifying Holder") will, if Registrable 
Securities held by the Indemnifying Holder are included in the securities as 
to which such registration, qualification, or compliance is being effected, 
indemnify the Company, each of its directors, officers, partners, legal 
counsel, and accountants and each underwriter, if any, of the Company's 
securities covered by such a registration statement, each person who controls 
the Company or such underwriter within the meaning of Section 15 of the 
Securities Act, each other such Holder (an "Indemnified Holder"), and each of 
their officers, directors, and partners, and each person controlling such 
Indemnified Holder, against all claims, losses, damages and liabilities (or 
actions in respect thereof) arising out of or based on any untrue statement 
(or alleged untrue statement) of a material fact contained in any such 
registration statement, prospectus, offering circular, or other document, or 
any omission (or alleged omission) to state therein a material fact required 
to be stated therein or necessary to make the statements therein not 
misleading, and will reimburse the Company and such Indemnified Holders, 
directors, officers, partners, legal counsel, and accountants, persons, 
underwriters, or control persons for any legal or any other expenses 
reasonably incurred in connection with investigating or defending any such 
claim, loss, damage, liability, or action, in each case to the extent, but 
only to the extent, that such untrue statement (or alleged untrue statement) 
or omission (or alleged omission) is made in such registration statement, 
prospectus, offering circular, or other document in reliance upon and in 
conformity with written information furnished to the Company by the 
Indemnifying Holder and stated to be specifically for use therein; PROVIDED, 
HOWEVER, that the obligations of the Indemnifying Holder hereunder shall not 
apply to amounts paid in settlement of any such claims, losses, damages, or 
liabilities (or actions in respect thereof) if such settlement is effected 
without the consent of such Holder (which consent shall not be unreasonably 
withheld); and PROVIDED FURTHER that the liability of an Indemnifying Holder 
pursuant to this Section 6(b) in connection with a registration shall be 
limited to the net proceeds from the sale of the Registrable Securities of 
such Indemnifying Holder pursuant to such registration.

          (c)  Each party entitled to indemnification under this Section 6 
(the "Indemnified Party") shall give notice to the party required to provide 
indemnification (the "Indemnifying Party") promptly after such Indemnified 
Party has actual knowledge of any claim as to which indemnity may be sought, 
and, except as provided in the following sentence, shall permit the 
Indemnifying Party to assume the defense of such claim or any litigation 
resulting therefrom; PROVIDED that counsel for the Indemnifying Party, who 
shall 

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<PAGE>

conduct the defense of such claim or any litigation resulting therefrom, 
shall be approved by the Indemnified Party (whose approval shall not 
unreasonably be withheld); PROVIDED FURTHER that the Indemnified Party may 
participate in such defense at its own expense; and PROVIDED FURTHER that the 
failure of any Indemnified Party to give notice as provided herein shall not 
relieve the Indemnifying Party of its obligations under this Agreement, to 
the extent such failure is not materially prejudicial. After the Indemnifying 
Party assumes the defense of such claim or litigation, the Indemnifying Party 
shall not be liable to the Indemnified Party under this Section 6 for any 
legal or other expenses subsequently incurred by such Indemnified Party in 
connection with the defense thereof, other than reasonable costs of 
investigation, unless the named parties to any such proceeding (including any 
impleaded parties) include both the Indemnified Party and the Indemnifying 
Party and representation of both parties by the same counsel would be 
inappropriate due to actual or potential differing interests between them.  
No Indemnifying Party, in the defense of any such claim or litigation, shall, 
except with the consent of each Indemnified Party, consent to entry of any 
judgment or enter into any settlement that does not include as an 
unconditional term thereof the giving by the claimant or plaintiff to such 
Indemnified Party of a release from all liability in respect to such claim or 
litigation.  Each Indemnified Party shall furnish such information regarding 
itself or the claim in question as an Indemnifying Party may reasonably 
request in writing and as shall be reasonably required in connection with 
defense of such claim and litigation resulting therefrom.

          (d)  If the indemnification provided for in this Section 6 is held 
by a court of competent jurisdiction to be unavailable to an Indemnified 
Party with respect to any loss, liability, claim, damage, or expense referred 
to therein, then the Indemnifying Party, in lieu of indemnifying such 
Indemnified Party hereunder, shall contribute to the amount paid or payable 
by such Indemnified Party as a result of such loss, liability, claim, damage, 
or expense in such proportion as is appropriate to reflect the relative fault 
of the Indemnifying Party on the one hand and of the Indemnified Party on the 
other in connection with the statements or omissions that resulted in such 
loss, liability, claim, damage, or expense as well as any other relevant 
equitable considerations.  The relative fault of the Indemnifying Party and 
of the Indemnified Party shall be determined by reference to, among other 
things, whether the untrue or alleged untrue statement of a material fact or 
the omission to state a material fact relates to information supplied by the 
Indemnifying Party or by the Indemnified Party and the parties' relative 
intent, knowledge, access to information, and opportunity to correct or 
prevent such statement or omission.

          (e)  Notwithstanding the foregoing, to the extent that the 
provisions on indemnification and contribution contained in the underwriting 
agreement entered into in connection with the underwritten public offering 
are in conflict with the foregoing provisions, the provisions in the 
underwriting agreement shall control.

          7.   INFORMATION BY HOLDER.  Each Holder of Registrable Securities 
shall furnish to the Company such information regarding such Holder and the 
distribution proposed by such Holder as the Company may reasonably request in 
writing and as shall be reasonably required in connection with any 
registration, qualification, or compliance referred to in this Agreement.

          8.   RULE 144 REPORTING.  With a view to making available the 
benefits of certain rules and regulations of the Commission that may permit 
the sale of the Restricted Securities to the public without registration, the 
Company agrees to use its best efforts to:

          (a)  make and keep public information regarding the Company available 
     as those terms are understood and defined in Rule 144 under the Securities 
     Act, at all times;

                                      -8-
<PAGE>

          (b)  file with the Commission in a timely manner all reports and other
     documents required of the Company under the Securities Act and the Exchange
     Act at any time after it has become subject to such reporting requirements;
     and

          (c)  so long as a Holder owns any restricted Registrable Securities,
     furnish to the Holder forthwith upon written request a written statement by
     the Company as to its compliance with the reporting requirements of Rule
     144, and of the Securities Act and the Exchange Act (at any time after it
     has become subject to such reporting requirements), a copy of the most
     recent annual or quarterly report of the Company, and such other reports
     and documents so filed as a Holder may reasonably request in availing
     itself of any rule or regulation of the Commission allowing a Holder to
     sell any such securities without registration.

          9.   TRANSFER OR ASSIGNMENT OF REGISTRATION RIGHTS.  The rights to 
cause the Company to register securities granted to Petro Star by the Company 
under this Agreement may be transferred or assigned by Petro Star with the 
related securities only to a transferee or assignee of not less than all of 
the Registrable Securities representing no less than 50% of the aggregate 
number of shares of Common Stock (as adjusted for any stock dividends, 
combinations or splits with respect to such shares) issued or issuable 
pursuant to the Warrant. Any transfer or assignment of the registration 
rights granted under this Agreement shall be conditioned upon (i) the 
Company's being given written notice at the time of or within a reasonable 
time after said transfer or assignment, stating the name and address of the 
transferee or assignee and identifying the securities with respect to which 
such registration rights are being transferred or assigned and (ii) the 
assumption in writing by the transferee or assignee of the obligations of a 
Holder under this Agreement.

          10.  ALLOCATION OF REGISTRATION OPPORTUNITIES.  In any circumstance 
in which all of the Registrable Securities requested to be included in a 
registration on behalf of the Holders cannot be so included as a result of 
limitations of the aggregate number of shares of Registrable Securities that 
may be so included, the number of shares of Registrable Securities that may 
be so included shall be allocated among the Holders requesting inclusion of 
shares pro rata on the basis of the number of shares of Registrable 
Securities held by such Holders.  The Company shall not limit the number of 
Registrable Securities to be included in a registration pursuant to this 
Agreement in order to include shares held by stockholders with no 
registration rights or, with respect to registrations under Section 2 hereof, 
in order to include in such registration securities registered for the 
Company's own account or securities other than Registrable Securities.

          11.  DELAY OF REGISTRATION.  No Holder shall have any right to take 
any action to restrain, enjoin, or otherwise delay any registration as the 
result of any controversy that might arise with respect to the interpretation 
or implementation of this Agreement.

          12.  TERMINATION OF REGISTRATION RIGHTS.  The right of any Holder 
to request registration or inclusion in any registration pursuant to Section 
2 or 3 hereof shall terminate on such date as all shares of Registrable 
Securities held or entitled to be held upon conversion by such Holder may 
immediately be sold under Rule 144(k).

          13.  MISCELLANEOUS.  

          13.1 GOVERNING LAW.  This Agreement shall be governed in all 
respects by the internal laws of the State of Delaware, without reference to 
the conflicts of law principles thereof.

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<PAGE>

          13.2 SUCCESSORS AND ASSIGNS.  Except as otherwise provided herein, 
this Agreement shall inure to the benefit of, and be binding upon, the 
successors, assigns, heirs, executors and administrators of the parties 
hereto.

          13.3 ENTIRE AGREEMENT. This Agreement constitutes the full and 
entire understanding and agreement between the parties with regard to the 
subjects hereof.

          13.4 NOTICES, ETC.  All notices and other communications required 
or permitted hereunder shall be in writing and shall be mailed by registered 
or certified mail, postage prepaid, or otherwise delivered by hand or by 
messenger, including Federal Express or similar courier services, addressed 
(a) if to a Holder, to Petro Star Inc., 201 Arctic Slope Avenue #200, 
Anchorage, Alaska 99518, Attn: President, or at such other address as such 
Holder shall have furnished to the Company in writing, or (b) if to the 
Company, to 4200 Research Forest Drive, The Woodlands, Texas, Attn:  
President, or at such other address as the Company shall have furnished to 
the Holders.  Each such notice or other communication shall for all purposes 
of this Agreement be treated as effective or having been given when delivered 
if delivered personally, or, if sent by mail or courier, at the earlier of 
its receipt or 48 hours after the same has been deposited in a regularly 
maintained receptacle for the deposit of the United States mail, addressed 
and mailed as aforesaid.

          13.5 COUNTERPARTS.  This Agreement may be executed in any number of 
counterparts, each of which may be executed by less than all of the Holders, 
each of which shall be enforceable against the parties actually executing 
such counterparts, and all of which together shall constitute one instrument.

          13.6 SEVERABILITY.  Whenever possible, each provision of this 
Agreement will be interpreted in such manner as to be effective and valid 
under applicable law, but if any provision of this Agreement is held to be 
invalid, illegal or unenforceable in any respect under any applicable law or 
rule in any jurisdiction, such invalidity, illegality or unenforceability 
will not affect such provision in any other jurisdiction, and this Agreement 
will be reformed, construed and enforced in such jurisdiction as if such 
invalid, illegal or unenforceable provisions had never been contained herein.

          13.7 TITLES AND SUBTITLES.  The titles and subtitles used in this 
Agreement are used for convenience only and are not to be considered in 
construing or interpreting this Agreement.

          13.8 AMENDMENT.  Except as expressly provided herein, this 
Agreement may be amended only upon the written consent of the Company and the 
Holders of at least seventy-five percent (75%) of the Registrable Securities 
then subject to this Agreement.







                                      -10-
<PAGE>

          IN WITNESS WHEREOF, this Agreement has been executed effective as 
of the date first set forth above.


                                        COMPANY:

                                        ENERGY BIOSYSTEMS CORPORATION


                                        By:
                                           -----------------------------------
                                        Name:
                                             ---------------------------------
                                        Title:
                                              --------------------------------



                                        PETRO STAR:

                                        PETRO STAR INC.


                                        By:
                                           -----------------------------------
                                        Name:
                                             ---------------------------------
                                        Title:
                                              --------------------------------




                                      -11-