Resolving the conflict between demands on organic wastes in rural Ethiopia - optimum solutions for food, energy and water security.

Background - In many areas of Sub-Saharan Africa, organic "wastes", including crop residues, food waste and excreta, are critical to food production, providing organic fertilisers for farmers who do not have the means to buy inorganic fertilisers, and reducing the need for irrigation by increasing the water holding capacity of the soil. However, these wastes also provide an important source of household energy. The way that organic wastes are used for energy directly affects both food and water security. Burning organic wastes removes carbon and nutrients, whereas residues from anaerobic digestion are nutrient-rich and can provide a valuable organic fertiliser as well as an energy source. Water quality can be improved by using organic wastes in energy production, so removing pathogens from the wider environment, but some energy technologies require extra water and so could impact the availability of water.
Finding efficient ways to use organic wastes is crucial to achievement of the post-2015 Sustainable Development Goals to eradicate poverty, improve food security and nutrition, promote sustainable agriculture, ensure sustainable management of water, and ensure provision of affordable energy. However, optimum use of organic wastes is highly context specific, depending on complex interactions between what science makes possible and how decisions are made by individuals. Determination of realistic measures requires input from farmers, industry, civil society, and local and regional policy makers. Enhancement of the efficiency of energy transformations becomes vital in socio-economic environments where there is competition for water and organic feedstocks.
Aim - to determine the how uses of organic wastes in rural areas of Southern Ethiopia impact food, energy and water security, and to design optimum solutions to improve access
Objectives - 1. Find out how organic wastes are currently used in rural areas of Southern Ethiopia and determine what alternative uses would be culturally acceptable;
2. Complete a lab-based analysis of exergy (energy that can be used), carbon, nutrient, water and pathogen for the full life cycle of the different uses of organic wastes;
3. Make recommendations for better uses of organic wastes to minimise loss of resources.
Methods
A combination of focus group discussions and surveys will be used to better understand how farmers in Southern Ethiopia are currently using organic wastes and the acceptability of new options for improved use of such wastes. Options to be considered will include
1. Energy release technologies (unimproved cookstoves / 3-stone fire; self-made improved cookstoves; pre-manufactured improved cookstoves; biogas digesters and gas stoves); and
2. Methods for using organic wastes as fertilisers (fresh wastes, composts, bioslurry and biochar).
Lab-based replicas of the different options for using organic wastes will be setup at UoA. The mass, energy and exergy balances will be studied, and carbon, nutrients, water and pathogens will be measured in samples of organic wastes, before and after treatment, losses being captured by analysis of any gases or liquids lost from the systems. Pathogens will be assessed by detection of faecal indicator organisms and clostridium. This analysis will follow the change in exergy, carbon, nutrients, water and pathogens from the initial organic wastes through the technology used to transform them, to the use of energy in cooking, and carbon and nutrients in organic fertilisers.
The results from the lab will be brought together in a systems model, describing the flows of exergy, carbon, nutrients, water and pathogens through different systems. This will allow the use of organic wastes to be optimized for different outcomes, and recommendations to be made for better use of organic wastes.