Composting
Carbon Sequestration and Greenhouse Gas Mitigation Potential of Composting and Soil Amendments on California’s Rangelands In one trial Mendocino had the highest increase in sequestration and range productivity of all the sites in the state
ABSTRACT Land management offers significant potential to both help lower greenhouse gas emissions and reduce atmospheric carbon dioxide. The goals of this research were to determine the short- and long-term potential of compost amendments to sequester carbon (C) in rangeland soil, and to determine the effects of future climate change scenarios on C storage and loss. The project also explored the emissions from the composting process itself, a poorly quantified component of the waste-to-rangeland lifecycle. Finally, the lifecycle emissions from rangeland compost amendments were compared to those of other fates of waste to determine potential benefits or tradeoffs among a range of common practices. Compost amendments (0.25 inch) to 15 diverse rangelands led to a detectable increase in surface (0-10 cm) soil C stocks (2.1 ± 1.0 Mg C ha-1) over a single growing season. The DayCent biogeochemical model was used to explore longterm effects of compost application in a subset of these rangelands, and to determine interactions with future climate change scenarios. Results showed that the overall climate benefit of compost amendments peaked 15 years after application. The benefit decreased over time, and decreased more quickly in a high emissions scenario. Two 100-day experiments using micrometeorological approaches yielded the first whole-pile, continuous measurements of greenhouse gas emissions from windrow composting. The total methane (CH4) emission factors were 0.6 and 0.7 g CH4 kg-1 feedstock, and were more sensitive to pile management than initial feedstock chemistry. Nitrous oxide emissions were below the instrument detection limit (25 ppb + 0.05%, or 4.5E-5 g m-2) throughout the experiments. A lifecycle assessment model suggested that diverting organic waste to composted field amendments resulted in greater CO2e savings compared to anaerobic digestion or incineration for energy, due to the combination of new C sequestration and emission reductions. In sum, results showed considerable potential for repurposing California’s organic waste-stream to compost for emissions reduction and C sequestration. Rangeland compost application, where appropriate, can contribute to climate change mitigation, as well as improve ecosystem productivity and sustainability.
Quantification of GHG for Compost Application- CARB study the sequestration estimate for Humboldt rangelands is 4 MT CO2e/acre/year
Results For each compost application implementation in Table 4, DNDC calculates changes in carbon dioxide (as SOC), nitrous oxide, and methane emissions per crop per county compared with the baseline scenario (i.e., no compost application). These results are further aggregated into emission reduction factors for the three broader crop categories of annual crops, trees/perennials, and grasslands, per county based on Table 1. Tables 5 through 11 show the final aggregated GHG reduction estimates for the seven compost implementation scenarios, respectively.
Abstract Direct emissions from commercial-scale composting are uncertain. We used micrometeorological methods to continuously measure greenhouse gas(CO2, CH4, N2O) emissions from full composting of green waste and manure. We measured oxygen (O2), moisture, and temperature continuously inside the composting pile, and analyzed chemical and physical characteristics of the feedstock weekly as potential drivers of emissions. Temperature, moisture, and O2 all varied significantly by week. Feedstock porosity, C:N, and potential N mineralization all declined significantly over time. Potential net nitrification remained near zero throughout. CH4 and CO2 fluxes, indicators of feedstock lability, were variable, and most emissions(75% and 50% respectively) occurred during the first three weeks of composting. Total CH4 emitted was 1.7 ± 0.32 g CH4 kg−1 feedstock, near the median literature value using different approaches(1.4 g CH4 kg−1 ). N2O concentrations remained below the instrument detection. Oxygen, moisture and temperature exhibited threshold effects on CH4 emissions. Net lifecycle emissions were negative (−690 g CO2-e kg−1 ), however, after considering avoided emissions and sinks. Managing composting piles to minimize methanogenesis—by maintaining sufficient O2 concentrations, and focusing on the first three weeks—could reduce emissions, contributing to the climate change mitigation benefit of composting.
Blake and Stephanie Alexandre along with their five children operate an organic dairy and pasture-raised chicken business on a total of 7,000 acres in three Northern California counties. They attribute the high level of involvement of their children in the family business to the fact that they have made it interesting by diversifying, bottling and marketing their own milk, and hosting youth programs on the farm. The AMMP
program will give them resources to upgrade some of their aging infrastructure. They will build a compost
bedded pack barn to house their young stock. Rather than flushing the manure out of the alleys with water, they will instead use large amounts of bedding to produce compost underneath the cows. They will combine this material with crab shells, fish waste and wood shavings from the area to enhance the compost, then apply it to their 3,000 acres of pasture to improve soil health. This system will keep their calves healthier during the wet winters, and enables them to build a new facility that is organized
and appropriately-sized.
The King County Biosolids Program monitors Loop’s physical, chemical, and microbial properties every month to make sure the product meets regulatory standards and is consistently high in quality. Less than 3 percent of the flow into King County’s treatment plants is from industrial sources, but to protect Loop’s quality, King County also works with local businesses and industries to make sure metals and chemicals stay out of the sewer. As a result, Loop contains very small amounts of metals—far less than the regulatory standards and similar to any other soil products on the market
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