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Frequently Asked Questions

Frequently Asked Questions


Q:What is G2G (Grass-2-Gas)?

A: Grass-2-Gas, or G2G, is a subset of the C-CHANGE project, focused on assessing whether perennial and winter crops can be more widely used as feedstock for producing renewable natural gas (RNG) through anaerobic digestion. The end goal is to create a market pull for farmers and farmland owners to establish more perennial and winter crops on their land and determine if the energetics make sense to replace usage of fossil natural gas with renewable natural gas developed from herbaceous material.

Q: What is feedstock?

A: A feedstock is the raw material used to create an energy source. In this case, the feedstocks are perennial and winter crops. However, in the larger context of biogas production, they may also include manure and food waste. 

Q: What are perennial grasses? When and where on the farm can they be planted?

A: Perennial grasses are resilient crops with many benefits and applications. They can be used for animal feed and bedding, and feedstock for RNG production, while also providing ecosystem benefits (e.g. reduced erosion, increased nutrient retention). They are best planted in areas on the farm that have resource concerns (e.g., areas prone to erosion, next to rivers and streams) or that yield poorly for annual crops (e.g., highly uneven terrain, frequently inundated areas, or turnrows).

While annuals, such as corn and soybeans, need to be replanted every year, perennials do not and thus provide an enormous cost-savings. Perennial grasses can be planted either in monocultures or in diverse mixtures, though diverse mixtures are preferred as they provide additional benefits as habitat for wildlife.

Q: What is a biobased value chain?

A: A value chain describes the full range of activities that an industry and its stakeholders do to bring a product from its conception to its end. More specifically, a biobased value chain is the network of businesses and job opportunities in rural areas that exist around energy production. It involves the production, collection, transportation, and conversion of that energy source, as well as its processing, distribution, and consumption.

In this context, a new biobased value chain is being created around the production of RNG, which can create new businesses and job opportunities for rural America.

Q:What is anaerobic digestion? How does it work?

A: Anaerobic digestion is the natural breakdown of organic matter by microorganisms in an environment without oxygen. These complex microbial communities break down – or digest – the organic matter, which in turn produces biogas.

Q: What is biogas? How does it become methane gas?

A: Biogas is about two-thirds methane and one-third carbon dioxide, and contains some other gases in trace amounts. Biogas can be cleaned and purified to become renewable natural gas, which is 98% methane.

Q: Isn’t methane gas even worse for the environment than carbon dioxide?

A: Uncaptured methane gas is 28 times as effective at capturing heat in the atmosphere compared to carbon dioxide. However, methane gas can be a sustainable energy source for vehicle fuel, electricity, and heat.

Q: What are the benefits of biogas?

A: Biogas helps improve resource management by capturing and utilize methane gas produced through the breakdown of organic matter, for example, in manure management, the processing of human waste, and from landfills. A large concern is landfilling food waste, and thus there is presently a lot of effort to divert this waste and either compost it or anaerobically digest it to produce biogas. Methane has 28 times the global warming potential as carbon dioxide. Since carbon dioxide is a co-product of anaerobic digestion, it can also be captured and used for food or industrial purposes, or geologically sequestered for long-term storage.

Q: Where is biogas already being generated?

A: Biogas is already being generated from through manure management, the processing of human waste, and at landfills.

Q: Who is funding this project?

A: The USDA awarded $10 million dollars over a five-year period through a grant from the National Institute of Food and Agriculture (NIFA).

Q: What is the timeline for this project?

A: The G2G project is a 5-year, USDA-funded project, spanning 2020-2025. Some preliminary outcomes are anticipated in 2023.

Q: Who are the primary stakeholders?

A: The partners include Iowa State University, Penn State University, Roeslein Alternative Energy, FDCE Inc., the USDA-ARS National Laboratory for Agriculture and Environment, as well as 33 other partner organizations.

Q: How does G2G improve the sustainability of the current agriculture system?

A: The program will work with farmers to incorporate perennial and winter crops into their operations. Not only will these additions help to produce a sustainable source of RNG, but they will also bring on-farm benefits such as decreased erosion, improved soil health, and increased nutrient retention.

Q: What happens with the biogas?

A: The biogas is cleaned and purified, becoming renewable natural gas (98% methane).

Q: Can anaerobic digestion be right-sized for individual farms?

A: Yes. The majority of farms have areas that yield poorly for annual crops. These areas could be losing money for the farm and, if converted to perennial and winter crops, will add value in terms of increasing soil health, retaining nutrients, protecting water quality, and providing habitat for wildlife. Improving the revenue stream associated with these areas is crucial to farmers. Improving the environmental benefits associated with these areas is crucial for society.

 Q: Who has the technical expertise to support the implementation of anaerobic digestion, at any scale?

A: AgStar, a division of the EPA, has a directory of organizations that support the installation and maintenance of anaerobic digester systems. That directory can be found here.

The American Biogas Council, a national trade association championing the growth of the biogas industry, also has a database of available businesses. That directory can be found here.

Q: Why does California's low carbon fuel standard (LCFS) matter so much?

A: The LCFS is designed to encourage the use of cleaner low-carbon transportation fuels in California, encourage the production of those fuels and, therefore, reduce GHG emissions and decrease petroleum dependence in the transportation sector. As the largest state economy in the US, California’s LCFS is an important driver of emerging renewable energy sources.