EPA sets a first in accurately accounting for GHG emissions from waste biofuel feedstocks

In a rule released last month, EPA became the first regulatory body to accurately account for greenhouse gas emissions (GHG) from displacing waste, residue, and byproduct biofuel feedstocks from pre-existing uses. While EPA, California’s Air Resources Board, and the European Union all acknowledge the substantial indirect GHG emissions that occur when food commodities are used for biofuel production, to date regulators haven’t counted indirect emissions from biofuel feedstocks that aren’t purpose-grown crops.

True wastes, like municipal solid waste or trap grease, can be used for biofuel production without any upstream or indirect emissions. Other materials that we typically think of as wastes are really byproducts used as inputs in manufacturing. For example, used cooking oil has historically been used in the U.S. as a livestock feed ingredient. Diverting it to biofuel production requires farmers to add more corn or vegetable oil to the feed to replace the lost calories. Producing the replacement corn or vegetable oil causes additional GHG emissions from farming and land use change, but regulators have ignored that source of emissions in past rulemakings.

The new rule concerns distillers sorghum oil used for biofuel production in the Renewable Fuel Standard (RFS). When sorghum grain is used to make ethanol, the distillers grains left over contain most of the oil and protein from the grain. The oil can be pressed out and sold. While it isn’t fit for human consumption, the distillers sorghum oil can be sold to biodiesel and renewable diesel producers. If the oil isn’t pressed out, it is fed to livestock as part of the distillers grains. Just like with used cooking oil, using distillers sorghum oil for biofuel leads to indirect emissions due to the additional corn or vegetable oil that is produced to supplement livestock feed and replace those lost calories.

Originally, EPA proposed to once again ignore indirect emissions from diverting distillers sorghum oil from livestock feed, similar to its decision on used cooking oil and tallow in a previous rulemaking. EPA argued that because dairy cattle produce better milk when fed low-fat diets, the efficiency improvement of feeding them low-fat sorghum distillers grains would offset the loss in calories. But, as we and a group of NGOs pointed out in public comments, the math didn’t add up. Even after accounting for the efficiency improvement of low-fat feed for dairy cattle, there would still be a calorie loss that would need to be made up with additional corn or another feed ingredient. In addition, sorghum distillers grains are likely fed to non-dairy cattle, pigs, and chickens, as well as dairy cattle. In its final rule, EPA cited our comments in its decision to count GHG emissions from displacing distillers sorghum oil from livestock feed. This change doubled the total GHG emissions accounted for in the sorghum oil biodiesel pathway, as shown in the graph below.

emissions from sorghum oil biodiesel

EPA counting indirect emissions for this pathway will likely not have a large impact in the near-term. Distillers sorghum oil biofuel still qualifies for use in biomass-based diesel in the RFS, which requires at least a 50% GHG reduction compared to fossil diesel. In addition, little distillers sorghum oil is currently produced in the US. However, this small change could lead to much bigger changes down the road.

In 2016, the last year for which data on poultry fat and tallow was available, 35% of US biodiesel was produced from wastes and byproducts. The list includes distillers corn oil, animal fats, and used cooking oil. If EPA reassesses waste and byproduct feedstocks from much larger biofuel production volumes, including distillers corn oil, animal fats, and used cooking oil, it could potentially have a much larger impact on the US biodiesel and renewable diesel market. And if California (where 93% of biodiesel and renewable diesel was produced from these feedstocks in 2017), the EU, or Canada decides to follow EPA’s example and begins to count indirect emissions from wastes, residues, and byproducts in their low carbon fuel policies, the regulatory impact could be very large indeed.

Fuels made from true wastes can deliver strong GHG savings without negatively impacting other uses. Cellulosic biofuels produced from sustainably harvested crop residues and energy crops grown on unused, low-carbon land may also play a prominent role in long-term transport decarbonization. The US, California, and EU have to date been providing similar policy incentives for biofuels made from true wastes and byproducts diverted from other productive uses. To drive the transition to very low carbon alternative fuels, policies should distinguish between the two. On this front, EPA has made an important step in the right direction.

Alternative fuels Life-cycle analyses
Fuels GHG emissions