Energy From Food Scraps
November 29, 2009
How does the program work and what are the benefits?
The program is designed to divert food scraps from disposal to land fills to a better use, which is the generation of clean energy. Specifically, in this first phase of implementation, we are piloting commercial food scraps from supermarkets, restaurants and food manufacturers. After the food scraps are collected, we separate and preprocess that material to remove what we call contaminants, put the material into our existing anaerobic digesters which generate methane gas – which we then burn in engines to create energy – and then send that energy to operate the waste water treatment plant which means less energy is pulled from the grid. As the program amps up, we anticipate becoming a net energy supplier of energy to others in the San Francisco Bay area.
In a typical composting system, what happens to the methane gas that is released as a byproduct of the process?
The anaerobic digestion process – where the food scraps go once they have been processed to remove contaminants – is a common one in the wastewater treatment industry. Organic material is pumped into large tanks that contain no oxygen, and the byproduct of the biological breakdown of the organic material is methane. Essentially, methane is natural gas, and we burn the gas to produce clean power. Right now, about 5% of the organic material comes from food scraps. The remaining material comes from solids that are a byproduct from the wastewater treatment plant. As we become more efficient in controlling contaminants, we hope to at least double our use of food scraps in the process. We think that our operation will eventually be cost competitive with alternatives that cities have for the disposal of garbage, and it will be sustainable. A sizable percent of material going to landfills is rich organic material that we could be using to extract clean energy.
What are the challenges of converting food scraps into energy?
Our biggest challenge in this process is contaminants. Contaminants are everything from plastic wrap to plastic bags, oyster shells to chopsticks, tin cans to metal twist ties – in other words, anything that isn’t food scraps. The challenge is figuring out how to mechanize and automate the separation process and make it efficient and effective. That’s at the heart of what we’ve been trying to do the last four to five years, and why not everyone is doing this yet. It’s a sole issue, but it’s formidable.
The question is where is the best place to do separation – at the source? Or at a central location? Part of our pilot program is working with haulers and participants to find that sweet spot, and to find the most overall cost effective place to do that separation.
How have you been able to merge commerce with sustainable business practices?
The profitability of this type of endeavor depends in part on the efficiency of the separation and the costs associated with it, as well as the premium value of renewable energy. We know that there is a lot of interest in wastewater and the garbage industry, and it does feel like there is this opportunity here to do good while doing good business.
How can retailers take advantage of this type of program?
If retailers in the San Francisco Bay area want to sign up, they can visithttp://www.wastediversion.org/ and get involved with the Contra Costa Solid Waste Authority. Hopefully, in the future, retailers in other areas will be able to participate in similar, local programs.
In upcoming issues, we will feature interviews with companies that are taking innovative steps toward the creation of sustainable products and services. If you are interested in telling us more about what your company is doing please contact Allison Bloom at firstname.lastname@example.org.