The city of Vancouver has pledged to become the greenest city in the world by 2020. To accomplish this goal, the city has identified three areas of focus, concentrating efforts on issues relating to carbon, waste, and ecosystems.
Food is one aspect of any city that relates to all three of these areas. Carbon from the processing and transportation of food, and emissions from livestock and the subsequent release of gasses from the decomposition of food waste are heavy contributors to global greenhouse gas emissions. Vancouver has vowed to increase city-wide food assets by 50% from 2010 levels, reducing dependance on foreign imports and Vancouver’s carbon footprint. To increase our food independence, vancouver is developing a municipal food strategy that incorporates all aspects of our food system. The strategy includes creating six new community gardens, three new urban farms, encouraging new farmers markets, and developing a Vancouver Food Hub.
The “Green Bin” program is also part of this strategy, addressing the issue of food waste, and realizing its position as an important part of the food system. The food we put in the Green Bin is turned into compost and can be purchased from the Vancouver landfill for a nominal $20 per tonne.
Vancouver’s food system is just one of the areas being targeted for reform by the city. The complete 2020 Vancouver Green Action Plan can be found here.
Another very cool waste conversion project was started by my good friend Rolf Eriksen, owner of the Happy Acres Sewage Processing Plant located on Orcas Island in Washington State. As a side business, Rolf began trucking sewage off Orcas, and bringing potable water onto the island (in different trucks of course) to augment the groundwater that often ran dry in the summer months. With the percent of actual “waste” in sewage being very small, in essence Rolf was transporting costly loads of water nearly 400 miles off the island to be spread on fields to decompose. Seeing as the island had chronic water supply shortages, this method of disposing of the island’s sewage did not seem practical, or economical. Coupled with rising disposal, fuel and ferry costs, Rolf decided their had to be an alternative way to deal with Orcas Island’s sewage that would be better for the environment, and make some money!
After doing some research and investing in the necessary equipment, a small sewage treatment plant was developed. At first, the process consisted of simply separating the solids (paper, bottle caps feminine hygiene products etc…) from the water.
Solid Separator
But it wasn’t simply the human waste and garbage that needed to be removed for the sewage to be turned into usable products. The problem was the heavy metals, pharmaceuticals, and toxic sanitation chemicals we flush down the pipe along with our waste. by injecting the filtered sewage with polymer compounds, the suspended solids bind together to form particles large enough to physically filter from the water.
The liquid that remains is water suitable for agricultural irrigation with biological content of 2 ppm. Most municipal water systems do not supply water this clean.
The biosolid component of this sewage is rich in nutrients, but also contains many pathogens that can cause illness and disease. These biosolids are difficult and expensive to transport to disposal facilities. As an alternative to disposal, Happy Acres decided to turn this solid waste into grade “A” fertilizer. By squeezing the biosolids through a “geotube” and removing any further water from the mixture. The remaining solids are left to compost with the addition of other organic material (leaf litter, wood chips…). The composting process generates temperatures of up to 151 degrees Fahrenheit, which, when harnessed, heats a nearby greenhouse.
As with most forms of waste, sewage is not an end product. It is a critical part of system that needs to be addressed, and not simply forgotten about after “the flush”. Rolf has not invented any new technology to carry out the treatment of raw septage. However, it is the fact that he has brought together different processes to show that waste can be turned into many useable products that benefit both humans and the environment.
Sewage is something that most people will be more than happy to keep out of sight and out of mind. But it should be looked upon as a crude substance, waiting for it’s usefulness to be realized.
