ARF11 - Optimizing energy production from anaerobically digested manure and co-substrates from medium size dairy farms

| Alternative Renewable Fuels - Project Summaries 2006 |

Researcher:

Anna Crolla, University of Guelph - Alfred Campus

Objectives:

1. Determine ideal co-substrates to enhance biogas production for medium size farm digesters in Ontario.
2. Evaluate enhanced biogas production through the addition of agricultural and non-agricultural co-substrates to manure, both at the lab and farm scales.
3. Evaluate economic and environmental benefits of anaerobic digester systems for medium sized livestock farms.
4. Develop and implement a technology transfer program that will foster the uptake of anaerobic digester systems to livestock operations in Ontario.

Expected Benefits:

This study will provide a reference for farms across Ontario considering the implementation of anaerobic digestion systems.  The use of co-substrates can significantly enhance biogas production from manure while helping to treat and dispose of some high strength wastes from the food processing industry.  The on-farm verification of economic, energy, nutrient and pathogen reduction benefits will assist in increasing the adoption of these technologies to medium sized livestock farms.  This project will provide comparative economic and environmental data from three anaerobic digester systems at medium size farms, presenting producers with clear information on the feasibility of each system.

Summary of Research Results:

The results from the preliminary lab (BMPs) study demonstrated that the mixture of manure with organic rich co-substrates resulted in higher biogas yields than the manure control (100% liquid dairy manure with inoculum). Corn silage at a mass ratio of 50% liquid dairy manure and 50% corn silage was highly effective and produced a biogas yield that was 1.6 times higher (0.657 m3 kg-1 TVS consumed) than the manure control. For the canola press cake it was determined that a ratio of 80% liquid dairy manure and 20% canola press cake produced a biogas yield of 0.769 m3 kg-1 TVS consumed; 1.9 times higher than the manure control digestion. A mixture of 70% liquid dairy manure and 30% whey resulted in a biogas yield of 0.652 m3 kg-1 TVS consumed which was 1.6 times higher than the manure control. A mixture of 40% liquid dairy manure and 60% FOG resulted in a biogas yield of 0.742 m3 kg-1 TVS consumed and was 1.8 folds higher than the manure control digestion.

The addition of 12% FOG in the Fepro Farm manure digester increased the organic loading rate to 3.096 kg TVS day-1 m-3, from a loading rate of 2.61 kg TVS day-1 m-3 (only manure) and increased the average biogas production by 2.9 folds. With the 12% FOG and 88% liquid dairy manure mixture the average biogas yield and electricity production of the digester was 0.732 ± 0.2 m3 kg-1 TVS initial and 1213 ± 329 kWh day-1, respectively. Terryland farm is also digesting a liquid dairy manure and FOG mixture at a mass ratio of 8% by mass FOG and 92% by mass liquid dairy manure. The FOG had a TVS content of 93% of the dry matter (TS) and the digester organic loading rate was 2.87 kg TVS day-1 m-3. The average biogas yield was determined to be 0.689 ± 0.3 m3 kg-1 TVS and the average daily electricity production was 1844 ± 765 kWh day-1.

The environmental benefits of anaerobically digesting manure include reduced odours and pathogens. The reduction of odours, measured as Total Volatile Fatty Acids (TVFA), at the Fepro farm digester was significant with and without the addition of the FOG; 98% and 95% removed, respectively. Pathogens reduction was also effective in the Fepro farm digester with a 3.29 log reduction of E.coli, a 0.92 log reduction of Salmonella, a 0.75 log reduction of C.perfringens and a 1.05 log reduction of Enterococci. The addition of 12% FOG maintained the pathogens reduction in the same log magnitude.

A comprehensive technology transfer plan had been implemented by the project partners during the study to ensure the dissemination of the project objectives and results. The project partners worked with OMAFRA personnel to inform industry stakeholders, like farmers and engineers, via workshops, tours, conference presentations on the evaluation of co-substrates for biogas yield enhancement.

Project Partners: University of Guelph, Ontario Ministry of Agriculture, Food and Rural Affairs, Agriculture and Agri-food Canada, University of Ottawa, Dairy Farmers of Canada, Fepro Farm, Terryland Farm and Pinehedge Farm.