Project Summary

Reducing household garbage and finding alternative energy sources are two main challenges facing our communities today. In this project, I examined the feasibility of creating an organic waste digester to be used in homes. The goal is to accelerate organic waste decomposition while capturing the biogas released and using it as a fuel source for furnaces.

In Phase 1 of this project last year, I tested if organic waste (in the form of sewage sludge) can release biogas in measurable amounts. I received valuable advice from panel experts emphasizing two areas of improvements: the method of gas measurement and the need for biogas analysis to confirm methane as a viable source of fuel. 

In Phase 2 this year, I devised methods to measure biogas via water displacement and analyze gas by conducting the Syringe Protocol**. I was also determined to maximize biogas production which I believe can be achieved by manipulating pH levels.  I hypothesized that segregating organic waste (food) by pH levels will result in the highest level of biogas production.

I used three food items to represent the various pH levels of neutral, acidic, and base.  I measured the amount and quality of the biogases released from each group and compared it against the biogas released by the combination of all three (Mixed substance). The neutral substances yielded the 10 - 30% more biogas than mixed, and the biogas consisted of 90% methane.  Whereas the acidic and base yielded 20 - 30% less.

With these new findings, I modified the first design of the household digester I developed. Instead of only having one compartment that combines food waste and sewage sludge, Ive added a secondary compartment that will allow base and acidic substances to neutralize before mixing with the sludge.  This digester will have a connection to the kitchen so that food waste can be easily dropped and a separate connection to allow controlled amounts of sewage sludge to come in.  There will be two output connections to the digester:  one for the methane captured directing it to the furnace, and one to flush remains out that can be used as fertilizers.


** Syringe Protocol by Mr. Paul Harris

Paul Harris (September 6, 2010) The Syringe Protocol. Retrieved: October 19, 2010, from



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