WHAT IS COMPOST?
Compost is the product of the natural process of decomposing and recycling organic matter - leaves, lawn clippings, food scraps - into a nutrient-rich soil amendment that helps plants grow. Microbes (bacteria, fungi), worms, and other decomposing organisms (sowbugs, nematodes) all help decompose organic matter. Many farmers call compost “black gold”.
Compost has numerous benefits. It reduces food and other organic waste (which makes up 28-50% of what is thrown away!). It reduces methane emissions from landfills, which are the third-largest source of human-generated methane emissions in the United States. Composting improves soil health and the water holding capacity of soil, conserving water. And compost adds carbon to soil, helping drawdown atmospheric carbon dioxide.
COMPOST IMPROVES SOIL HEALTH AND INCREASES SOIL CARBON STORAGE
Soil too sandy? Too clayey? Poor in nutrients? Not draining well? Not holding
enough water? Too compacted?
Compost can solve all these and more!
One of the primary reasons people add compost to soil is because it is rich in
nutrients. When you grow plants, they use nutrients like nitrogen and phosphorus, and over time, the soil can become depleted of nutrients. Compost uses the natural process of decomposition to put nutrients back into the soil.
Compost improves soil structure, helping soils form aggregates, or assembled soil particles of sand, silt, and/or clay, held together by organic matter and microbes. These aggregates reduce soil compaction and erosion. They create more pore spaces, or holes in soil, and more connected pores. This allows better flow of water and makes it easier for plant roots to grow.
Aggregates with organic matter are also good at holding on to water, so that in a sandy soil, the water does not all just pour through before the plants can take it up. For every 1% increase in organic matter, which comes from sources like compost amendments, available water in soil can increase by 20,000 gallons per acre!
Compost not only is made by microbes; it also helps support an abundant and diverse microbial community in soil, which in turn makes the soil healthier and the plants growing in that soil healthier. A recent study from 2021 showed that as compost matures, there are more beneficial microbes present in the compost. Compost also provides a carbon and nutrient rich food source for microbes.
Compost adds carbon to soil, helping to increase soil organic matter. Compost is a critical component of regenerative agriculture, restoring organic matter to soil that was lost through intensive land use practices like deforestation and industrial agriculture. Soils have the potential to store more carbon, helping drawdown atmospheric carbon dioxide. Composting takes organic matter that would have contributed to methane and carbon dioxide emissions from a landfill and instead puts it in the soil where a portion of that carbon can be stored for up to thousands of years. A full-life cycle analysis of compost production and application through the Marin Carbon Project in northern California found that “composted manure and plant waste led to large offsets that exceeded emissions, saving upwards of 55 Metric Tons of CO2 per acre per year.”
METHODS FOR MAKING COMPOST
Making compost at home can be easy! At its simplest, it is a pile of food and yard
waste. Add to the top, and in about a year, you will have soil at the bottom!
If you are excited about making “the perfect” compost, there are several more
The “ideal” compost has the following ingredients: carbon, nitrogen, oxygen, phosphorus, potassium, trace minerals (like calcium and iron), and a pH between 5.5 - 8.5. Vegetable scraps, coffee grounds, grass clippings, and manure are all high in nitrogen. These are what some people call your “greens”. Autumn leaves, straw, wood chips, sawdust, bark, mixed paper, newspaper, and corrugated cardboard are all high in carbon. These are what some people call your “browns”. An “ideal” carbon-to-nitrogen (C/N) ratio for compost is 30:1, which is 30 parts carbon for each part nitrogen by weight. To achieve this, many people advise about half “greens” and half “browns”. This C/N ratio favors bacteria that help heat up to the compost. Oxygen concentrations of greater than 10% (the atmosphere is 21% oxygen) are optimal.
To achieve this “perfect” compost, some people will make sure to balance additions of different materials. Some people “turn” their compost, either with a shovel when it is in a pile, or with cylindrical composting tumblers to increase oxygen.
A fluffy layer of browns at the bottom of a compost pile can help absorb moisture and increase oxygen.
Ideally, compost is moist - not too wet or too dry.
Some people use thermometers, microbial inoculants, and additions of things like kelp. But for most people, just using food and yard scraps is just fine for making great compost.
Vermicomposting is a way of composting with worms. When worms decompose organic matter, they create vermicasts, which are rich in nutrients. Vermicomposting is faster than conventional composting. If you chose to do vermicomposting, it is important that you trust your worm source and make sure you are using red wigglers so that you are not adding invasive species. Vermicomposting can reduce soluble salts in compost, which is sometimes an issue in compost made from manure or mushrooms.
Compost tea is a liquid compost, with soluble plant nutrients and beneficial microbes. To make compost tea, you mix compost with water, either with or without aeration. It can be used as a soil drench or foliar application.
The Lincoln transfer station has a Black Earth compost dropoff. Lincoln residents can also pay for Black Earth compost pick up. They are able to compost items that you might not want to compost at home including dairy products, meat, bones, seafood, shells, paper napkins, paper towels, and BPI, CMA, or OK Compost/TUV certified compostable serviceware. (Note: no waxed cardboard, milk cartons, paper cups not certified compostable, junk mail, grass clippings unless subscribed to “organic lawn care partners”.)
HOW AND WHEN TO APPLY COMPOST
You can add compost at the beginning and end of the growing season and any
time you are harvesting one crop and planting a new one. Compost can be used on garden beds, spread over lawns, and as a mulch. Broad forks can help gently mix compost with soil
COMPOSTING IN LINCOLN
Black Earth Compost dropoff is available for free at the Lincoln Transfer station. You can compost yard and/or food waste. Black Earth Compost also offers curbside pickup for a charge.
Cornell is a fantastic resource for composting: http://www.compostcornell.org/
Black Earth Compost, which is what we have at the Lincoln Transfer Station: https://blackearthcompost.com/
Institute for Self-Reliance’s resources on “Composting for Community”: https://ilsr.org/composting/
A nice recent article in the New York Times: https://www.nytimes.com/2023/01/01/headway/composting-food-leftovers.html
US Environmental Protection Agency Resources: https://www.epa.gov/recycle/composting-home
Natural Resources Defense Council Resources: https://www.nrdc.org/stories/composting-101
The Marin Carbon Project has researched the impact of adding compost to soil and found exciting results about increased carbon storage: https://marincarbonproject.org/compost/
K. Paustain, E. Larson, J. Kent, E. Marx and A. Swan. "Soil C Sequestration as a biological negative emission strategy." Frontiers in Climate 16, 2019, doi:10.3389/fclim.2019.00008.
J. Sanderman, T. Hengl, and Gregory J. Fiske. "Soil carbon debt of 12,000 years of human land use." Proceedings of the National Academy of Sciences 114 (36) 9575-9580, 2017, doi:10.1073/pnas.1706103114.
D.A. Bassio, S.C. Cook-Patton, P.W. Ellis, J. Fargione, J. Sanderman, et al. 2020. "The role of soil carbon in natural climate solutions." Nature Sustainability 3, 391–398, 2020, doi:10.1038/s41893-020-0491-z