In the past, livestock manure was highly shunned, not only for its stench but also for its methane emissions. However, in recent years, it has become a commercially viable source of biogas for power generation and, through purification, renewable natural gas (RNG). Besides being sold as regular natural gas, RNG also offers an environmental bonus by reducing methane emissions, earning it the nickname "brown gold" in foreign media.
However, climate experts and advocates worry that turning manure brown and gold will incentivize ranches to expand, defeating the original purpose of reducing methane emissions.
RNG, touted as a more sustainable energy source, has become a hot energy source, with oil companies increasing their investment.
The Guardian reports that investment in converting manure into energy has increased rapidly in the United States over the past few years. This growth has been particularly pronounced in states with strong livestock production, such as California, Wisconsin, and New York. The passage of the Inflation Reduction Act last year (2022), which introduced several incentives for renewable energy and carbon reduction measures, has further fueled this business.
In California, for example, more than 100 publicly funded anaerobic manure digestion facilities were under construction and expected to be operational by the end of 2022. In 2021, the number of RNG facilities planned for the U.S. livestock and agricultural sectors (both planned and already in operation) increased by over 36% compared to the previous year.
Methane emissions are a major concern in the livestock industry. Both animal burps and the decomposition of manure in storage tanks release methane, the second-most potent greenhouse gas contributing to global warming, with a warming potential 28–36 times greater than that of carbon dioxide. In the past, animal manure was often used to generate biogas for power generation. In recent years, purifying the methane in animal manure to produce RNG has become a new sustainable option for many businesses.
In 2021, US logistics giant UPS pledged to purchase 250 million gallons of RNG over the next seven years, making it the largest consumer of RNG in the transportation industry. UPS's head of fleet procurement noted that purchasing RNG will help the company achieve its sustainability goals.
In October 2022, BP announced its $4.1 billion acquisition of Archaea Energy, a US RNG producer. In November, a subsidiary of oil and gas giant Shell acquired Nature Energy, Europe's largest RNG and biomethane producer, aiming to enter the global RNG business. Shell expects the acquisition to generate a "double-digit return" for the company.
Climate groups worry about ranches profiting from manure
As RNG becomes increasingly popular, environmental and climate groups are concerned about potential backfires. Methane from livestock farms comes primarily from two sources: manure and cow burps. According to The Guardian, these two sources contribute roughly the same amount of methane in California, and RNG can only utilize methane from manure. In other words, half of the methane problem remains unsolved.
Researchers worry that incentives for methane capture are so attractive that they could make manure the main commodity on farms, with dairy products becoming a byproduct.
Kevin Fingerman, an associate professor at California Polytechnic State University (Cal Poly Humboldt), was commissioned to conduct the analysis. His findings, published in 2022, suggest that for medium- and large-scale ranches in California, methane capture could, in some cases, represent approximately 40% of total profitability. The study warns that when methane capture revenue exceeds that of dairy production, ranches may increase the number of animals they keep to produce more manure.
Source: Environmental Information Center (https://e-info.org.tw/node/236073)
