Livestock manure is transformed into a bioresource enriched with carbon in just one day

Newswise — A technology has been developed to quickly convert livestock manure, a significant issue in animal farming, into valuable "black gold" rich in carbon within a day.

Dr. Yoo Ji-ho and his research team from the Clean Air Research Laboratory of the Korea Institute of Energy Research (hereafter referred to as 'KIER') have developed a process that immediately converts livestock manure into biochar* at livestock farms. Using the process developed by the research team, it is possible to convert 10 tons of livestock manure into biochar in a single day.
* Biochar: A compound word of 'biomass' and 'charcoal', this material is produced by pyrolyzing organic matter such as the stalks of grains, animal excreta, and food waste under oxygen-limited conditions at temperatures above 350℃. When biomass is decomposed by soil microorganisms, it is released into the atmosphere in the form of carbon dioxide or methane. However, when biomass is converted into biochar, up to 80% of the carbon contained in the biomass can be sequestered within the biochar, earning it the nickname 'carbon prison'.

As of 2022, the amount of livestock manure produced was about 50 million tons, of which 87% is used as compost and liquid fertilizer after being fermented over a long period. However, during this long treatment process, which can last more than 60 days, nitrous oxide (N2O), a greenhouse gas 300 times stronger than carbon dioxide, is emitted. Additionally, ammonia (NH3), which causes ultrafine dust and odors, is also released, accounting for 70% of the total emissions nationwide. This has led to persistent odor complaints, becoming a chronic problem for livestock farmers.
* "In 2021, out of a total of 23,511 odor complaints, 13,616 cases, or 58% of the total, were related to the livestock sector (according to the Ministry of Environment's odor complaint statistics).

Biochar is gaining attention as an alternative solution to overcome these issues. Converting livestock manure into biochar not only completely prevents the emission of nitrous oxide and ammonia but also absorbs carbon from the air and can sequester it, making it a viable means to achieve carbon neutrality in the livestock sector. Consequently, the government has designated biochar as a core technology area for carbon neutrality in the livestock sector and plans to expand the use of biochar and improve manure management in livestock farms through the 'Livestock Sector 2030 Greenhouse Gas Reduction and Green Growth Strategy'.
* To reduce greenhouse gas emissions in the livestock sector, farms will be equipped with greenhouse gas reduction facilities, and the proportion of livestock manure purification and energy facilities will be expanded. By 2030, it is expected to reduce the livestock sector's greenhouse gas emissions by 30% (3.2 million tons) compared to projected levels (Ministry of Agriculture, Food and Rural Affairs, January 3, 2024).

The core of the MTB* process developed by the research team is a dehydration and drying technology that reduces the moisture content in livestock manure, which is over 80%, to less than 20%. The research team successfully designed and built an integrated system that combines the drying process owned by the KIER, the dehydration process from the Korea Institute of Machinery and Materials (KIMM), the pretreatment process from DULI TECH Co., Ltd., and the pyrolysis technology from YOUGI IND Co., Ltd. to achieve optimal performance. Using this, the overall energy consumption can be significantly reduced to less than one-tenth compared to the conventional rotary kiln method.
* Manure To Biochar: An integrated process of dehydration, pretreatment, drying, and pyrolysis for converting livestock manure into biochar.

The process begins with a screw-type solid-liquid separator developed by the KIMM. This separator reduces the moisture content in livestock manure, which is over 80%, to less than 60%. The energy used in this step is minimized to 1% of that used in conventional heat-based processes like the rotary kiln method (horizontal, cylindrical). The separated manure chunks are then finely crushed to less than 1 cm in size by a three-stage blade crusher developed by DULI TECH Co., Ltd.
*F-COMB (Flexible-Counter flOw Multi-Baffle): A high-energy efficiency drying/pyrolysis device that maximizes contact between solids and counterflow hot air through multiple zigzag-arranged baffles in a reverse flow multi-flexible baffle reactor.
*TLUD (Top Lid Up-Draft): A system where ignition starts from the top and burns downward while the smoke rises upward, reaching temperatures of 350 ℃ in the dried livestock manure, undergoing pyrolysis to produce biochar.

This process has been demonstrated at a pilot site in Cheongyang County, Chungnam, capable of handling 10 tons of livestock manure per day. The research team successfully completed 100 hours of process operation, proving its commercial viability. In particular, the F-COMB drying device developed by the KIER is highly competitive in terms of energy efficiency, production cost, and convenience. Plans are in place to scale up to more than 100 tons per day to meet domestic demand as well as international demand from China, Australia, and Indonesia, who are pushing for environmentally friendly waste management and recycling.

Most of the livestock manure in Korea is being composted, and there is a lack of measures to reduce the greenhouse gases and ultrafine dust particles that are emitted during this process. The process we developed is a low-cost, high-efficiency process that can immediately convert livestock manure into biochar on-site, serving as a key technology to prevent environmental problems in the livestock sector and emissions of greenhouse gases.

This research was conducted as part of the Ministry of Science and ICT's Fundamental Technology Development Project, in collaboration with the KIMM, DULI TECH Co., Ltd., YOUGI IND Co., Ltd., Chilseong Energy, and Chungnam National University.