With many of the country's Gulf Coast and Mid-Continent refineries offline due to the storm, there was a significant 60 million barrel drawdown of surplus product inventories in the U.S., bringing product inventories to normal levels.
Our wholesale operations also continue to see positive trends in U.S. demand, and we expanded our supply into Mexico with current sales of over 60,000 barrels per day, which should continue to increase with the ramp-up of supply through the Vera Cruz terminal.
The system is expected to be capable of storing 5 million metric tons of CO2 per year.
In our Diamond Green Diesel 2 project at St. Charles remains on budget and is now expected to be operational in the middle of the fourth quarter of this year.
The expansion is expected to increase renewable diesel production capacity by 400 million gallons per year, bringing the total capacity at St. Charles to 690 million gallons per year.
The expansion will also allow us to market 30 million gallons per year of renewable naphtha from DGD 1 and DGD 2 into low-carbon fuel markets.
The renewable diesel project at Port Arthur or DGD 3 continues to move forward as well and is expected to be operational in the second half of 2023.
With the completion of this 470 million gallons per year capacity plant, DGD's combined annual capacity is expected to be 1.2 billion gallons of renewable diesel and 50 million gallons of renewable naphtha.
We're already seeing a strong recovery in gasoline and diesel demand at 93% and 100% of pre-pandemic levels, respectively.
For the first quarter of 2021, we incurred a net loss attributable to Valero stockholders of $704 million or $1.73 per share, compared to a net loss of $1.9 billion or $4.54 per share for the first quarter of 2020.
The first quarter 2021 operating loss includes estimated excess energy costs of $579 million or $1.15 per share.
For the first quarter of 2020, adjusted net income attributable to Valero stockholders was $140 million or $0.34 per share.
The adjusted results exclude an after-tax lower of cost or market, or LCM, inventory valuation adjustment of approximately $2 billion.
The refining segment reported an operating loss of $592 million in the first quarter of 2021, compared to an operating loss of $2.1 billion in the first quarter of 2020.
The first-quarter 2021 adjusted operating loss for the refining segment was $554 million, compared to adjusted operating income of $329 million for the first quarter of 2020, which excludes the LCM inventory valuation adjustment.
The refining segment operating loss for the first quarter of 2021 includes estimated excess energy cost of $525 million related to impacts from Winter Storm Uri.
Refining throughput volumes in the first quarter of 2021 averaged 2.4 million barrels per day, which was 414,000 barrels per day lower than the first quarter of 2020 due to scheduled maintenance and disruptions resulting from Winter Storm Uri.
Throughput capacity utilization was 77% in the first quarter of 2021.
Refining cash operating expenses of $6.78 per barrel were higher than guidance of $4.75 per barrel, primarily due to estimated excess energy costs related to impacts from Winter Storm Uri of $2.21 per barrel.
Operating income for the renewable diesel segment was a record $203 million in the first quarter of 2021, compared to $198 million for the first quarter of 2020.
Renewable diesel sales volumes averaged 867,000 gallons per day in the first quarter of 2021.
The ethanol segment reported an operating loss of $56 million for the first quarter of 2021, compared to an operating loss of $197 million for the first quarter of 2020.
The operating loss for the first quarter of 2021 includes estimated excess energy costs of $54 million related to impacts from Winter Storm Uri.
First quarter of 2020 adjusted operating loss, which excludes the LCM inventory valuation adjustment, was $69 million.
Ethanol production volumes averaged 3.6 million gallons per day in the first quarter of 2021, which was 541,000 gallons per day lower than the first quarter of 2020.
For the first quarter of 2021, G&A expenses were $208 million and net interest expense was $149 million.
Depreciation and amortization expense was $578 million, and the income tax benefit was $148 million for the first quarter of 2021.
The effective tax rate was 19%.
Net cash used in operating activities was $52 million in the first quarter of 2021.
Excluding the favorable impact from the change in working capital of $184 million and our joint venture partner's 50% share of Diamond Green Diesel's net cash provided by operating activities, excluding changes in DGD's working capital, adjusted net cash used in operating activities was $344 million.
With regard to investing activities, we made $582 million of total capital investments in the first quarter of 2021, of which $333 million was for sustaining the business, including costs for turnarounds, catalysts and regulatory compliance, and $249 million was for growing the business.
Excluding capital investments attributable to our partner's 50% share of Diamond Green Diesel and those related to other variable interest entities, capital investments attributable to Valero were $479 million in the first quarter of 2021.
On April 19, we've sold a partial membership interest in the Pasadena marine terminal joint venture for $270 million.
Moving to financing activities, we returned $400 million to our stockholders in the first quarter of 2021 through our dividend.
And as you saw earlier this week, our board of directors approved a regular quarterly dividend of $0.98 per share.
With respect to our balance sheet at quarter end, total debt and finance lease obligations were $14.7 billion and cash and cash equivalents were $2.3 billion.
The debt-to-capitalization ratio net of cash and cash equivalents was 40%.
At the end of March, we had $5.9 billion of available liquidity, excluding cash.
We expect capital investments attributable to Valero for 2021 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.
For modeling our second-quarter operations, we expect refining throughput volumes to fall within the following ranges: Gulf Coast at 1.65 million to 1.7 million barrels per day; Mid-Continent at 430,000 to 450,000 barrels per day; West Coast at 250,000 to 270,000 barrels per day; and North Atlantic at 340,000 to 360,000 barrels per day.
We expect refining cash operating expenses in the second quarter to be approximately $4.20 per barrel.
With respect to the renewable diesel segment, with the start-up of DGD 2 in the fourth quarter, we now expect sales volumes to average 1 million gallons per day in 2021.
Operating expenses in 2021 should be $0.50 per gallon, which includes $0.15 per gallon for noncash costs such as depreciation and amortization.
Our ethanol segment is expected to produce 4.1 million gallons per day in the second quarter.
Operating expenses should average $0.38 per gallon, which includes $0.05 per gallon for noncash costs such as depreciation and amortization.
For the second quarter, net interest expense should be about $150 million, and total depreciation and amortization expense should be approximately $590 million.
For 2021, we still expect G&A expenses, excluding corporate depreciation, to be approximately $850 million, and the annual effective tax rate should approximate the U.S. statutory rate.
Lastly, as we reported last quarter, we expect to receive a cash tax refund of approximately $1 billion later this year.

Summary:
The renewable diesel project at Port Arthur or DGD 3 continues to move forward as well and is expected to be operational in the second half of 2023.
For the first quarter of 2021, we incurred a net loss attributable to Valero stockholders of $704 million or $1.73 per share, compared to a net loss of $1.9 billion or $4.54 per share for the first quarter of 2020.
The first quarter 2021 operating loss includes estimated excess energy costs of $579 million or $1.15 per share.
For the first quarter of 2020, adjusted net income attributable to Valero stockholders was $140 million or $0.34 per share.
Refining throughput volumes in the first quarter of 2021 averaged 2.4 million barrels per day, which was 414,000 barrels per day lower than the first quarter of 2020 due to scheduled maintenance and disruptions resulting from Winter Storm Uri.
The debt-to-capitalization ratio net of cash and cash equivalents was 40%.