Dr. Sally Brown

Organic residuals, soil health and
greenhouse gases

Organic residuals, such as biosolids and compost from food waste, have the potential to improve soil fertility and a number of other soil properties important for plant growth. Organic residuals and soils can also play a role in climate change: The different end-use options available for organic residuals can carry very different total life-cycle greenhouse gas emissions, and soils can be important sources and sinks of greenhouse gases when applied with residuals. Soils applied with residuals may also tend to store more carbon, making them an important tool in mitigating human-driven climate change. We have conducted research into the carbon storage potential of soils applied with organic residuals (including biosolids), and have also begun work on establishing the strength of nitrous oxide (N₂O) emissions from organically amended soils.

Field studies

• Vashon Island Nitrous Oxide Study. A study of land reclamation at a former borrow pit on Vashon Island (Washington) directly monitoring N₂O emissions from soils applied with different amendments, including biosolids composts.


• "Land application of organics: Quantifying greenhouse gas, soil and water benefits": Field study of farm soils applied with compost or biosolids showing improved soil carbon and nitrogen, reduced bulk density, and increased water availability with organics. Project of former graduate student Kate Kurtz (MS). Final report: Land Application: A true path to zero waste? Results of biosolids and compost application presented to Washington State Department of Ecology by S. Brown and K. Kurtz.


• "Carbon sequestration in reclaimed soils": Field study comparing conventionally reclaimed former mine soils to mine soils reclaimed with biosolids. Demonstrated increased carbon storage in biosolids-reclaimed soils, even 20-30 years after final reclamation. Project of former graduate student Andrew Trlica (MS). Executive Summary (pdf).


• "Changes in soil properties and carbons sequestration potential as a result of compost or mulch application: Results of on-farm sampling": Results of field study on life-cycle benefits to soil of compost use on agricultural soils in California. The study tracked benefits in total organic carbon, microbial activity, water holding capacity, water infiltration rate, bulk density and nutrient availability.


• "Biosolids for Biodiesel": Phase I report on biosolids used as fertilizer for canola which can then be used to make biodiesel to support local mass transit. Winner of the 2005 Leader in Biosolids Green Globe Award.


• "Fuel from Food Waste": Laboratory study on the potential for using the anaerobic digestion process on food waste mixed with biosolids to enhance natural gas production at wastewater treatment facilities.

Review papers

• "Methane Avoidance from Composting": Issue paper for the Climate Action Reserve covering existing research and quantification approaches avoided methane emissions with diversion of food waste to compost rather than landfilling.


• "The Biosolids Emissions Assessment Model (BEAM): A method for determining greenhouse gas emissions from Canadian biosolids management practices": Prepared for the Canadian Council of Ministers of the Environment. A review of the scientific literature on greenhouse gas emissions potential from biosolids, and emissions calculator model for greenhouse gas inventories.

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