In addition to be made into fertilizers, pig excrement can be used to generate power that can be exchanged for carbon credits. Hanbao Livestock Farm in Fangyuan Township, Chunghwa County has about 40,000 heads of pig. It treats its pig excrement via anaerobic fermentation and uses the biogas produced from the treatment process to generate electricity. It also installed solar panels on the roofs of pig sheds to generate energy. The farm applied to register for the EPA’s greenhouse gas (GHG) offset program. It completed registration on 20 March 2020 and became the first livestock farm in Taiwan that successfully registered for the voluntary GHG offset program. Its annual GHG reduction is expected to reach 27,541 metric tons of CO2e, and its total carbon credits over the seven-year-long program is estimated to amount to 192,787 metric tons of CO2e.
The EPA said that currently most of the pig excrement goes through three stages of treatment: solid-liquid separation, anaerobic fermentation, and aerobic aeration. Among these stages, aerobic aeration requires tremendous amount of electricity, and the anaerobic fermentation generates biogas which is rich in methane, a substance with a global warming potential 21 times higher than carbon dioxide and hence contributing more to global warming. Therefore, livestock wastewater treatment processes generate massive amounts of GHG and cause severe impact on the global climate.
Hanbao Farm generates roughly 1,810 metric tons of livestock excrement every day. It collects the biogas generated from the anaerobic fermentation and removes the sulfides before using the biogas to generate electricity, reaping double carbon reduction benefits. Reduction of fugitive methane results in lower GHG emission equivalent to 23,900 metric tons of CO2, and using the collected methane instead of fossil fuels for power generation further reduces GHG emission equivalent to 1,930 metric tons of CO2. The farm also installed solar panels on the expansive roofs of pig sheds to generate green energy, further cutting down emission by 1,800 metric tons of COe.
The Greenhouse Gas Offset Program Management Regulations (溫室氣體抵換專案管理辦法) was formulated by the EPA to encourage enterprises to adopt reduction measures. Enterprises can apply to register for a GHG offset program with their emission reduction proposals. After the registration is approved, they can further apply for GHG reduction credits based on actual reductions. With measures like collecting biogas for energy generation and solar power in place, Hanbao Farm was able to apply to implement a GHG offset program, which was reviewed and approved. After the registration was completed, the farm has become the first livestock farm in Taiwan that has completed a GHG offset program registration, and is now qualified to apply for reduction credits.
Livestock excrement can go through ananerobic fermentation to produce digestate sediment and fluid, which can be used to fertilize farmland instead of being discharged directly into surface water bodies. This way not only can river pollution be reduced, the digestate sediment and fluid, which are rich in nitrogen and phosphate and more soil-friendly than chemical fertilizers, can also replace chemical fertilizers and hence help to reduce soil acidification and increase production yields and quality. Every year Hanbao Farm sends its roughly 10,000 metric tons of digestate sediment and fluid via irrigation pipes to fertilize 4.17 hectares of foxtail grass farms. Foxtail grass is a main crop for herbivore livestock like cattle and sheep and is also one of the best fiber supplements for pigs. Moreover, Hanbao Farm treats its solid excrement left behind after solid and liquid separation via aerobic aeration indoors instead of by anaerobic fermentation outdoors. This also lowers the chance of methane escaping into the air and is expected to achieve an annual carbon reduction of 3,158 metric tons of CO2e. The farm has applied for GHG offset program registration for this practice.
Excerpt from Environmental Policy Monthly, 23 (9)
- Environmental Protection Administration, R.O.C.(Taiwan)