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Podcast: Cooking, Cooling and Cultivating with Waste

Published: Monday, 27 Mar 2017
Author: Katie Deska
Department: Global Center for Food Systems Innovation

When properly processed, decomposing human and animal waste has the power to change lives. While it might sound – and smell – funny, the power of poop lies in biogas, a renewable energy source produced during anaerobic digestion, or the breakdown of waste. Sped up through a system of digesters, the process yields a gas of about 60 percent methane that can be used for cooking, refrigeration, and other basic needs. Moreover, the waste itself can be processed and applied to fields to enrich the soil and improve crop production. 

Researchers Rebecca Larson, assistant professor at the University of Wisconsin-Madison, and Vianney Tumwesige, CEO of Green Heat, a Ugandan energy company, teamed up on a host of projects in Kampala, Uganda that demonstrate new ways to transform waste to resource. Funded through the Global Center for Food Systems Innovation (GCFSI), the team developed and continues to evaluate a biogas-powered refrigeration unit; a waste separation system that yields no-cost fertilizer; and a dual-fuel stove that cuts down on deforestation while easing cooking challenges.

Listen to an interview with Larson, hosted by reporter Pechulano Ali, of the Food Fix, a multimedia project launched through GCFSI.

Traditionally, the cook at Kampala's Lweza Primary School prepared meals for the students over a wood-burning stove. While reliable, the smoldering indoor fire caused poor air quality in the kitchen and contributed to the relentless harvest of timber. Seeking an alternative, the school switched to a biogas-powered stove, but struggled with the problem of burning through the biogas supply before the food was fully cooked.

To solve the problem, Larson and researchers designed a second-generation biogas stove that has the option to run on biogas or firewood. With the grant from GCFSI, the team refined the design and settled on a solution that gives the user flexibility to switch from biogas to firewood, or vice versa. Since being provided with the new duel-fuel stove, Lweza Primary School is able to improve indoor air quality and reduce wood consumption.

Building on the success of the duel-fuel stove, a team member from Green Heat modified a natural gas-powered refrigeration unit to run on biogas, which is cheaper and more accessible than natural gas. Like the stove, the modified cooler can run on more than one source of energy. "If you run it on biogas first, you can switch to electricity, and if the electricity goes out, you can switch to biogas," said Larson. In a region that has unpredictable electrical service, multiple power options provides increased dependability.

But, harvesting the potential of waste doesn't stop there – the waste itself can be put to use. 

The team in Kampala successfully implemented a new low-cost slurry separation system that divides liquid waste, called effluent, from solid waste. Once the separated solids are dried, they can be applied to fields to enrich crop production. More desirable to handle than raw manure, and more economically viable than purchasing chemical fertilizers, the separated solids are a good alternative for cash-strapped farmers.

"The solid-liquid separator is very popular. We installed 50 of the systems. We designed it, and with this (GCFSI) grant we refined our design," said Larson. "Green Heat built their inventory and have been installing them in Uganda, and will install some in Ethiopia. A lot of people weren't managing the effluent, and it was going to the wastewater treatment, or worse off, running into a stream. We wanted a system to allow them to better manage the effluent from the digester."

With the systems installed and refinements made, the team is busy evaluating performance and determining best practices for field application, water conservation, and other considerations.

Field data on the impact of separated solids on agricultural plots shows promise. Findings indicate that while actual grain production is consistent across different nutrient sources, use of separated solids on maize increases plant biomass, like leaves and stalks, which can be fed to livestock, or used to generate more biogas – continuing the cycle.


Housed within MSU's department of International Studies and Programs, the Global Center for Food Systems Innovation addresses critical pressures on the world's food supply by creating, testing and enabling the scaling of solutions. GCFSI takes a multidisciplinary approach that encompasses the entire food system and considers major environmental, economic and social trends, as well as workforce development needs that will impact future food security. Launched in 2012, GCFSI is one of eight development labs established through the Higher Education Solutions Network of the United States Agency for International Development.