“Fueling the Future” is a recurring segment on our blog where we feature the work of companies and organizations that are working today to provide the energy sources of tomorrow.

Would you ever think that the banana peel you are holding in your hand could be used to keep your lights on? Or that your wilted lettuce could be used to provide heat and electricity for the entire neighborhood? We’re not talking about the absurd organic fusion reactor that the Doc uses to power the DeLorean’s flux capacitor; we’re talking about a real-life process for converting organic waste into electricity.

Anaerobic digestion (AD) is a process utilized by farmers, waste management companies, and cities to produce energy from organic waste. The process begins by collecting organic waste, such as food scraps or yard waste, and loading it into storage tanks called anaerobic digesters. The tanks seal out oxygen, allowing bacteria to decompose the waste anaerobically (without oxygen). This process results in the production of methane which can then be burned to generate electricity and heat. As a side bonus, the solid waste leftover after the microbes have had their fill can be used as agricultural quality compost.

An interior shot of one of ZWE’s dry anaerobic digesters. The sprinklers at the top of the chamber release a constant spray of percolate, a watery substance containing microbes that break down the organic waste.

One of the companies pioneering this method of waste-to-energy is called Zero Waste Energy (ZWE), based in San Jose, CA. Since their founding in 2009, the company has made significant strides in diverting organic waste from California’s landfills and using it in anaerobic digesters that incorporate their own SMARTFERM technology. ZWE’s proprietary SMARTFERM technology utilizes a dry AD process that minimizes the need for water and input energy.

These efficiency improvements are made possible by using aerobic digestion, the same process that takes place inside a compost pile, to heat up the organic waste. As the oxygen is depleted, anaerobic bacteria take over and start producing biogas (methane and carbon dioxide) at an accelerated rate due to the additional heat. Using this process, it takes just 21 days to complete energy extraction and to convert the remaining solid waste into digestate (compost yet to be dried). This is a 25% improvement in productivity compared to other dry systems.

Zero Waste Energy's first AD facility built in Marina, CA.

Zero Waste Energy’s first AD facility built in Marina, CA.

The company currently operates two different AD facilities, one in Marina, CA and another within the city of San Jose that started up last December. The new San Jose facility is the largest dry AD plant in the world and represents a joint venture between GreenWaste Recovery, Zanker Road Resource Management, and ZWE. The facility is built with 16 AD digesters capable of processing 90,000 tons of organic waste per year. The total methane output of the plant is enough to generate 1.6 MW of electricity using dual 800 kW heat and energy generation systems. All told, the San Jose AD facility has the capacity to divert 85% of the city’s organic waste from landfills, meeting California’s mandate for diverting a majority of municipal organic waste from landfills by 2020.

An exterior shot of ZWE's San Jose AD facility.

An exterior shot of ZWE’s San Jose AD facility, the largest dry AD plant in the world.

ZWE is currently in the process of building additional waste processing facilities in California, Alabama, and Doha, Qatar. In California specifically, the company is building a new facility in South San Francisco to process organic waste into compressed natural gas, or CNG. The gas produced by the facility will be used to power a fleet of 12 collection vehicles, each of which will be able to carry enough organic waste from just one route to fuel it for an entire day. This will effectively create a closed-loop system, allowing the facility to generate all the electricity needed for normal operation, as well as providing all the fuel for its collection vehicles.

Other North American projects include a new materials recovery facility, or MRF, to serve the city of Montgomery, AL. The facility is a partnership between local developer IREP and Bulk Handling Systems, the company providing the equipment for the recovery of recyclable materials. The MRF is designed as a single stream processing center, allowing residents of Montgomery to dispose of their trash in a single container that is then sorted at the facility. Recyclables, organics, and general refuse are separated using a variety of machinery and equipment, greatly increasing the recovery rate of recyclable materials.  ZWE will run the MRF, as well as integrate one of their own SMARTFERM dry anaerobic digestion systems that will produce CNG and compost for later sale. Once the facility is up and running, it will achieve a waste diversion rate of 95%. That translates to 225,000 tons of municipal solid waste processed every year.

Zero Waste Energy’s work with organics promises to change the way we manage our waste, as well as the methods by which we generate our electricity. Removing organics from the waste stream curbs greenhouse gas emissions from landfills, as well as provides a reliable source of renewable energy. For each of these reasons, future generations will look back and wonder why it took us so long to discover just how useful our food scraps and lawn clippings can be.