(CN) — Researchers at Cornell University have an idea, and they’re not just slinging a line of bull: They plan to produce renewable energy from cattle manure to both heat buildings through the freezing winter months and reduce the campus’ carbon footprint.
According to a study published Tuesday in the Journal of Renewable and Sustainable Energy, agricultural waste could help the university in its efforts to produce entirely clean energy.
Cornell is striving to meet the demands for energy on its campus while also adapting to the need for clean energy sources in the face of climate change, aiming to be 100% carbon neutral by the year 2035. Members of the Cornell University Senior Leaders Climate Action Group have been proposing solutions since 2016 and have introduced ideas such as elevating building energy standards, replacing all campus-owned vehicles with a clean energy fleet, and educating students on climate literacy.
By 2019, Cornell had already reduced its emission levels by 36%. The university divides its carbon usage into different categories, including on-site combustion of fossil fuels, electricity supply and consumption, and university-related travel. One of its main focuses has been reducing methane leakage from natural gas, which it has identified as having the biggest impact on climate change.
The university’s main campus in Ithaca, New York, has proven to be the most troublesome in energy efficiency, particularly in the winter season. Ithaca’s temperatures in January average between a low of 19 degrees Fahrenheit and high of 39 degrees Fahrenheit, requiring constant heating of Cornell’s buildings, labs, and dormitories. With 46% of Cornell’s undergraduate students living on campus, the winter months require a great deal of energy to provide adequate heating to all of its residents.
One project in the works to provide heat while reducing the amount of energy needed is a geothermal heating approach, in which there will be a hot water supply approximately two miles underground. This approach would sustainably warm the school under normal conditions, but the authors of the study said that it would be inefficient for more severe weather conditions.
To fight winter’s chill, the research team hopes to rely on the school’s Dairy Center of Excellence, a farm that is home to about 600 cows. This agricultural waste energy method extracts methane and other usable products from the cows’ manure in a three-stage process.
The first stage occurs when the manure is digested within the cows and the result is biogas, a renewable fuel that consists of various gases, including methane and carbon dioxide, that can be captured and utilized. Capturing biogas that escapes through animal waste and cow flatulence helps combat greenhouse gas emissions and, according to the U.S. Environmental Protection Agency, can provide a cost-effective source of renewable energy for electricity, heating and transportation fuel.
The second stage involves converting the manure into a form of bio oil, a product achieved by drying, heating and altering the state of the organic matter. Previous studies analyzing the potential of bio oil have found that dry manure contains the potential for 12 to 18 gigajoules per ton. According to Canada's Office of Energy Efficiency, one gigajoule of electricity can power a 60-watt light bulb for six months.
Another product of this stage is hydrochar. Like bio oil, hydrochar is an efficient and cost-effective source of fuel and can also be used to revive damaged soil.
The third stage of the method produces renewable natural gas, or RNG, that can be used as a complete energy source. Here, the carbon dioxide captured from the biogas in the first method is combined with hydrogen gas obtained through a process called electrolysis, in which water is split into hydrogen and oxygen. This process is made renewable by collecting water from nearby lakes.
The authors say that if this renewable natural gas were to be injected into New York’s natural gas grid, it could produce energy similar to the way wind turbines and solar panels collect electricity.
"The proposed system will produce about 909 million liters of RNG per year," said author Nazih Kassem, a doctoral candidate in biological & environmental engineering at Cornell. "This can provide 97% of the total annual peak heating demand. The remainder can be met by purchasing natural gas, increasing Cornell's dairy herd size, or using campus eateries' food wastes for co-digestion. Adding 19 more dairy cows would result in enough RNG production to meet the average annual peak heating demand."
This study highlights the need for further research and investment in renewable natural gas, and the authors hope their proposal will encourage policymakers to turn their attention to this avenue of renewable energy.
"If New York state were to adopt policies to create a carbon market and enable competitive RNG pricing, then the proposed biomass peak heating system would show profitability," Kassem said.
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