We also saw a significant jet fuel recovery as domestic and international travel opened up, increasing from approximately 60% of pre-pandemic levels at the beginning of the year to approximately 80% at the end of the year.
In addition, the Diamond Green Diesel expansion project, DGD 2, commenced operations in the fourth quarter on budget and ahead of schedule.
The expansion has since demonstrated production capacity of 410 million gallons per year of renewable diesel as a result of process optimization, above the initial nameplate design capacity of 400 million gallons per year.
This expansion brings DGD's total annual renewable diesel capacity to 700 million gallons.
Looking ahead, the DGD 3 project at our Port Arthur refinery is progressing ahead of schedule and is now expected to be operational in the first quarter of 2023.
With the completion of this 470 million-gallon per year plant, DGD's total annual capacity is expected to be 1.2 billion gallons of renewable diesel and 50 million gallons of renewable naphtha.
Valero is expected to be the anchor shipper with 8 ethanol plants connected to this system, which should provide a higher ethanol product margin.
In 2021, we took measures to reduce Valero's long-term debt by approximately $1.3 billion.
We ended the year well capitalized with $4.1 billion of cash and $5.2 billion of available liquidity, excluding cash and our net debt to capitalization was 33%.
We continue to honor our commitment to stockholders, defending the dividend across margin cycles and delivering a payout ratio of 50% in 2021.
And as recently announced, the board of directors has approved a quarterly dividend of $0.98 per share for the first quarter of 2022.
For the fourth quarter of 2021, net income attributable to Valero stockholders was $1 billion or $2.46 per share compared to a net loss of $359 million or $0.88 per share for the fourth quarter of 2020.
Fourth quarter 2021 adjusted net income attributable to Valero stockholders was also $1 billion or $2.47 per share compared to an adjusted net loss of $429 million or $1.06 per share for the fourth quarter of 2020.
For 2021, net income attributable to Valero stockholders was $930 million or $2.27 per share compared to a net loss of $1.4 billion or $3.50 per share in 2020.
2021 adjusted net income attributable to Valero stockholders was $1.2 billion or $2.81 per share compared to an adjusted net loss of $1.3 billion or $3.12 per share in 2020.
The refining segment reported $1.3 billion of operating income for the fourth quarter of 2021 compared to a $377 million operating loss for the fourth quarter of 2020.
Fourth quarter 2021 adjusted operating income for the refining segment was $1.1 billion compared to an adjusted operating loss of $476 million for the fourth quarter of 2020.
Refining throughput volumes in the fourth quarter of 2021 averaged 3 million barrels per day, which was 483,000 barrels per day higher than the fourth quarter of 2020.
Throughput capacity utilization was 96% in the fourth quarter of 2021 compared to 81% in the fourth quarter of 2020.
Refining cash operating expenses of $4.86 per barrel in the fourth quarter of 2021 were $0.46 per barrel higher than the fourth quarter of 2020, primarily due to higher natural gas prices.
The renewable diesel segment operating income was $150 million for the fourth quarter of 2021 compared to $127 million for the fourth quarter of 2020.
Adjusted renewable diesel operating income was $152 million for the fourth quarter of 2021.
Renewable diesel sales volumes averaged 1.6 million gallons per day in the fourth quarter of 2021, which was 974,000 gallons per day higher than the fourth quarter of 2020.
The higher operating income and sales volumes were primarily attributed to the start-up of Diamond Green Diesel expansion project DGD 2 in the fourth quarter.
The ethanol segment reported record operating income of $474 million for the fourth quarter of 2021 compared to $15 million for the fourth quarter of 2020.
Adjusted operating income for the fourth quarter of 2021 was $475 million compared to $17 million for the fourth quarter of 2020.
Ethanol production volumes averaged 4.4 million gallons per day in the fourth quarter of 2021, which was 278,000 gallons per day higher than the fourth quarter of 2020.
For the fourth quarter of 2021, G&A expenses were $286 million and net interest expense was $152 million.
G&A expenses of $865 million in 2021 were largely in line with our guidance.
Depreciation and amortization expense was $598 million and income tax expense was $169 million for the fourth quarter of 2021.
The annual effective tax rate was 17% for 2021, which reflects the benefit from the portion of DGD's net income that is not taxable to us.
Net cash provided by operating activities was $2.5 billion in the fourth quarter of 2021 and $5.9 billion for the full year.
Excluding the favorable impact from the change in working capital of $595 million in the fourth quarter and $2.2 billion in 2021 and the other joint venture members' 50% share of Diamond Green Diesel's net cash provided by operating activities, excluding changes in DGD's working capital, adjusted net cash provided by operating activities was $1.8 billion for the fourth quarter and $3.3 billion for the full year.
With regard to investing activities, we made $752 million of total capital investments in the fourth quarter of 2021, of which $353 million was for sustaining the business, including costs for turnarounds, catalysts and regulatory compliance and $399 million was for growing the business.
Excluding capital investments attributable to the other joint venture members' 50% share of Diamond Green Diesel and those related to other variable interest entities, capital investments attributable to Valero were $545 million in the fourth quarter of 2021 and $1.8 billion for the year.
We returned $401 million to our stockholders in the fourth quarter of 2021 through our dividend and $1.6 billion through dividends in the year, resulting in a 2021 payout ratio of 50% of adjusted net cash provided by operating activities for the year.
And our board of directors recently approved a regular quarterly dividend of $0.98 per share, demonstrating our sound financial position and commitment to return cash to our investors.
With respect to our balance sheet at year-end, total debt and finance lease obligations were $13.9 billion and cash and cash equivalents were $4.1 billion.
The debt-to-capitalization ratio net of cash and cash equivalents was 33%.
In the fourth quarter, we completed a series of debt reduction and refinancing transactions that together reduced Valero's long-term debt by $693 million.
These debt reduction and refinancing transactions, combined with the redemption of $575 million floating rate senior notes due 2023 in the third quarter, collectively reduced Valero's long-term debt by $1.3 billion.
At the end of the year, we had $5.2 billion of available liquidity, excluding cash.
We expect capital investments attributable to Valero for 2022 to be approximately $2 billion, which includes expenditures for turnarounds, catalysts and joint venture investments.
About 60% of our capital investments is allocated to sustaining the business and 40% to growth.
Approximately 50% of our growth capital in 2022 is allocated to expanding our low-carbon businesses.
For modeling our first quarter operations, we expect refining throughput volumes to fall within the following ranges: Gulf Coast at 1.66 million to 1.71 million barrels per day, Mid-Continent at 395,000 to 415,000 barrels per day, West Coast at 185,000 to 205,000 barrels per day and North Atlantic at 430,000 to 450,000 barrels per day.
We expect refining cash operating expenses in the first quarter to be approximately $4.80 per barrel.
With respect to the renewable diesel segment, we expect sales volumes to be approximately 700 million gallons in 2022.
Operating expenses in 2022 should be $0.45 per gallon, which includes $0.15 per gallon for noncash costs such as depreciation and amortization.
Our ethanol segment is expected to produce 4.2 million gallons per day in the first quarter.
Operating expenses should average $0.44 per gallon, which includes $0.05 per gallon for noncash costs such as depreciation and amortization.
For the first quarter, net interest expense should be about $150 million and total depreciation and amortization expense should be approximately $600 million.
For 2022, we expect G&A expenses, excluding corporate depreciation, to be approximately $870 million.

Summary:
For the fourth quarter of 2021, net income attributable to Valero stockholders was $1 billion or $2.46 per share compared to a net loss of $359 million or $0.88 per share for the fourth quarter of 2020.
Fourth quarter 2021 adjusted net income attributable to Valero stockholders was also $1 billion or $2.47 per share compared to an adjusted net loss of $429 million or $1.06 per share for the fourth quarter of 2020.