The use of renewable energy in the agricultural industry is an exciting new frontier that, with the right partners, can bring environmental and economic benefits to farmers, surrounding communities and the renewable transportation fuels industry. And it really revolves around manure.
The use of livestock manure is nothing new. Historically, it is a proven agricultural method for improving soil quality to help crops grow. Using manure as a natural fertilizer also keeps carbon in the soil and out of the atmosphere, where it can form carbon dioxide (CO2), a greenhouse gas (GHG). This is essential, as agriculture accounts for 11% of total GHG emissions. Add to that the transport and electricity industries which account for 27% and 25% of GHG emissions respectively, and we are looking at nearly two-thirds of the causes that contribute to climate change.
Fortunately, these emissions can all be reduced using technology that already exists. Through the use of biodigesters, agricultural manure can be converted into renewable natural gas (RNG) and the leftovers into valuable materials including fertilizers, drinking water and CO2.
Anaerobic digestion
According to the United States Environmental Protection Agency (EPA), an anaerobic biodigester is a system that uses organic waste to produce fertilizer and biogas or renewable fuel (Figure 1). It is usually an airtight container made of high-density polyethylene that uses anaerobic digestion, a fermentation process devoid of oxygen. The process separates the methane from the solids and liquids that make up the manure while effectively preventing the smell from escaping into nearby communities. The methane captured at the top of the biodigester containers can then be used to create RNG.
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1. The process of energy recovery from waste is quite simple. Manure undergoes anaerobic digestion to produce biogas, which is processed and upgraded to renewable natural gas and digestate. Courtesy: EnTech Solutions |
The process begins when animal manure is deposited into anaerobic biodigesters. When held at a temperature of 100F, biodigesters create an environment where microbes grow and consume volatile solids from manure while producing methane.
The extracted methane gas can be reused in various ways. It has traditionally been used to generate electricity through fuel-powered generator engines, but it can also be used to produce clean GNR fuel. RNG is an essential part of a clean energy future as it is an efficient alternative to fossil natural gas. The cow manure conversion process is carbon negative and equates to a carbon intensity (CI) score of almost 300 negative.
RNG can be injected into a pipeline and used in the transportation industry for cleaner burning vehicles. This is especially important for vehicle fleets in states like California, Oregon, Washington, and New York, all of which have regulations requiring companies to use cleaner-burning vehicle fuels. The use of RNG reduces pollution and allows organizations in the transport sector to meet these requirements. Research shows that when all climate benefits are considered together, RNG from dairy manure can reduce GHG emissions by up to 400% when used to replace traditional vehicle fuels.
Investing in anaerobic biodigesters also benefits the agricultural industry. Local farmers who send their manure to an anaerobic biodigester facility reap the benefits of various nutrient streams once the manure is processed. Once the methane is extracted, nutrient concentration systems can further break down the manure to remove pathogens like phosphorus that previously contaminated nearby water sources.
The end product of the solid fiber material is sent back to farmers for use as compost and bedding, saving them the hassle of buying sawdust, wood chips, straw or sand. Additionally, through nutrient concentration systems, the liquid material can be further separated into a concentrated liquid fertilizer that farmers can use in their fields. This leaves evacuable water through streams that can either return directly to the local water system or be used by local farms for irrigation or livestock.
The future is now in Wisconsin
When we say “farms of the future”, we actually mean now. This biodigester technology is in use at a facility in Middleton, Wisconsin, located just outside the state capitol (Figure 2). The project is a remarkable example of what the agricultural industry can achieve today.
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2. EnTech Solutions owns and operates a biodigester facility in Middleton, Wisconsin. The majority of the facility’s electricity comes from an on-site solar plus battery micro-grid. Courtesy: EnTech Solutions |
EnTech Solutions, a clean energy provider, and Northern Biogas, a digester and RNG development company, have partnered with local farmers and Dane County to reuse a biodigester that previously generated electricity. The Middleton facility includes three anaerobic biodigesters that break down manure from four local dairy farms.
In 2021, more than 27 million gallons of manure were processed by the facility and more than 57,000 pounds of phosphorus was removed from the Yahara watershed, a natural drainage system in southern Wisconsin. The partnership also includes Aqua Innovations Nutrient Concentration System and US Gain as the purchaser of the RNG.
This self-sustaining network benefits farmers who can better manage their animal waste, prevent the release of methane into the atmosphere, and receive the resulting nutrient-rich materials for their fertilizer and bedding (Figure 3). It benefits the county and the community by reducing phosphorus runoff to nearby streams and lakes. And it benefits the renewable transportation fuels industry with the RNG created by the extracted methane.
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3. The remaining result of anaerobic digestion is digestate that can be used as animal bedding and fertilizer. At Middleton Digester, the digestate is thoroughly dried before being sent back for further use on local farms. Courtesy: EnTech Solutions |
Help improve farm profitability
Beyond these benefits, the Middleton facility has also been strategically upgraded to run on renewable energy. EnTech Solutions powers the Middleton facility using distributed energy in the form of a microgrid powered by rooftop and ground mounted solar panels and battery storage. The solar power system generates over 2.8 MW of clean energy, which could power over 400 homes. This effectively reduces emissions by more than 13,500 metric tons per year of CO2 equivalent, which amounts to eliminating nearly 34 million kilometers traveled by cars.
The more layers of renewable energy incorporated into the RNG creation, the greater the GHG reduction impact and the lower the IC score. For example, if RNG was transported using fleets of electric vehicles powered by renewable electricity, this would further reduce the environmental impact. By generating and using renewable energy in the facility through solar technology and microgrids, EnTech Solutions lowers the RNG’s CI score, making it cleaner and more valuable.
The long-term benefits also continue to accrue to farmers. Transforming farm operations preserves the way of life of farm families while solving many of the problems they face. Advanced anaerobic biodigesters open the door to more revenue from crops and dairy, as well as increased production of manure converted into RNG, fertilizer and bedding, creating an easier path to agricultural growth.
The anaerobic biodigester facility in Middleton, Wisconsin is an excellent example of what the farms of the future can look like. Using renewable energy, even at the scale of an industrial facility, is a self-sustaining model that can be replicated in communities across the country.
Cows produce manure – it’s nothing new – but now the technology exists to reap the benefits of this waste with anaerobic biodigester plants, nutrient concentration systems and renewable energy sources, enabling clean operations carbon neutral or even carbon negative. These state-of-the-art facilities allow farmers to continue to manage their operations while ensuring that they are more environmentally conscious. We have said that these are the farms of the future, but in reality, this future is now.
The question of how to produce enough food to feed a growing global population while simultaneously reducing the carbon footprint of operations is an ongoing challenge for consumers and policy makers, and one that is multi-faceted. The energy experts at EnTech Solutions remain committed to supporting the dairy industry as a solution provider in the global quest to achieve net neutrality. The opportunity exists to create economically viable options for agricultural waste management that can be easily replicated and that can provide solutions to a number of waste-related challenges facing the industry.
Based on feedback from various stakeholders, this project was a resounding success for everyone involved. Positive community impacts include improved environmental watershed by more reliably removing phosphorus from agricultural runoff. City and county officials shared that this process has become a source of pride that other municipalities would like to emulate.
In December 2021, EnTech Solutions received a Climate Champion award from the Dane County Office of Energy and Climate in recognition of our concrete and innovative steps towards climate success in the county. On the farm, the image and reputation of dairy farming in this region is greatly enhanced by shifting public perception from dairy farming contributing to the GHG problem to farmers actively working to address climate change issues.
—Scott Romenesko is President of EnTech Solutions.
