Biogas and fertilizer in a new age

| April 16, 2012
Full-scale anaerobic digester. Photo: kqedquest/Flickr

The use of biogas as a fuel in Sweden suggests that there is a replacement for fuel oil that is derived from wastes buried -- often deep in earth -- by ecological processes of decomposition and storage. Before learning that burning oil and coal would lead to severe planetary problems, we proceeded with ignorance of the consequences: witness damage to oceans, atmosphere, incidence of severe storms, imminent threat to slippage of Greenland's ice mass and similar problems with Antarctic ice masses.

Imagine a world in which most nations could be self-sufficient by distilling their own fuels. Imagine the benefits of eliminating fuel oil spills in the oceans. Imagine small producers making fuel affordable for transportation, heating homes, or production of electricity.

In sustainability-conscious Sweden, the city of Stockholm has converted its 1,600 vehicles to running on biogas. The private market for biogas-fuelled cars is increasing. Anaerobic digestion of sewage sludge has been carried on for decades and the resulting biogas is used for heating, electricity production, and is processed for car fuel. The biogas is manufactured from organic wastes from restaurants and commercial kitchens as well as from manure and sewage. The waste product from the biogas production is better as fertilizer than ordinary manure because it makes nitrogen is more available.

In Linkoping, a city of 140,000, a plant was started in 1997 to treat organic agricultural waste in southeastern Sweden. It provides biogas for urban city buses and reduces emissions from urban transport. The plant treats 100,000 tonnes annually and produces 4.7 million cubic metres of upgraded biogas (97 per cent CH4 ) that is used in 64 buses and a number of heavy and light duty vehicles.

The first biogas train ran between Linkoping and Vastervik in June 2005. The biogas run train has reduced its greenhouse gas emissions to zero.

The Nordic nations are obviously offering sustainability options we would do well to adopt -- if we truly seek to create a world where democratic options are still acceptable.

In Europe, the Swedish National Government and the European Union have passed laws that give guidance to communities regarding solid waste disposal and recycling. In Sweden, laws require communities to be responsible for natural resource preservation. In 1995 each national department, including forestry, fisheries, agricultural planning and housing was instructed to prepare an action plan for preserving biodiversity. In 1998 the European Union Commission also presented a strategy for protecting biodiversity throughout the European Union.

Individual communities in Canada acting on their own initiative have undertaken sewage recycling, Kelowna and Vernon being good examples in British Columbia. But the impetus that could be given by a federal government interested in the sustainability of our society is sadly lacking.

In Western Canada, the city of Calgary can be proud of the fact that it recycles approximately 355,000 cubic metres of sewage daily; returning purified water to the Bow River, and fertilizer to farm land within a 60- to 70-kilometre radius of the city. A realistic philosophy places the cost of processing ($150 per tonne) as part of the cost of urban life.

Wastewater is treated through a biological process. It undergoes primary and secondary treatment, is heated to 33 degrees C to kill any pathological bacteria, and finally subjected to ultraviolet light before the excess water is removed and returned to the Bow River. It is also passed through a process which removes many of the heavy metals. The remaining sludge is passed into lagoons and holding ponds where more settling takes place, and more wastewater is removed.

According to plant management, what remains is a liquid product containing between 8.5 per cent and 12 per cent solid material. This sludge is moved to nurse tankers, which are located at farmers' fields. Large machines called Terragators pick up the sludge from the nurse tankers and then apply it to the land by injecting the liquid fertilizer between 2 to 4 inches into the soil where it is readily available to the roots of plants. Injecting the product into the soil reduces problems of runoff or potential smell.

The product can be injected into an individual field every three years, to a maximum (at present) of four applications. Each field receives an average of 7 tonnes per hectare. Prior to application, the soil is tested and farmers may be told that it is advisable to apply lime which helps to neutralize the soil. The soil is also tested after each application.

Through the use of GIS imagery, a computer on-board the Terragator contains a map of each field being fertilized. The computer records exactly which areas of the field have received the application. Any areas missed accidentally, or because of an obstacle such as a slough or building, show up on the map as white areas, while those areas receiving the fertilizer show up as black. The farmer can be supplied with a map clearly showing which areas have been fertilized. There is a remarkable difference in the quality and quantity of growth between the black areas which have received the application and white areas which have not, and farmers are virtually "standing in line" for the Calgro product, which they receive free of charge.

An added benefit of the wastewater treatment at the Calgary Fish Creek and Bonnybrook plants is the fact that all of the biogas emanating from the sewage sludge is captured and fed to four large generators which produce 80 per cent of the electricity needed by the processing plants.

This is a remarkable sustainable success story, and one which puts to shame cities like Victoria, B.C., which still dumps 120 million litres daily of filtered raw sewage into the ocean. Despite the fact that this sewage contains 3 gms a day of PCBs, according to a Sierra Club report, the B.C. government has said that Victoria will be allowed to continue doing so until a greater environmental need appears. While Halifax and St. John's also dump raw sewage straight into the ocean, 87 other Canadian municipalities still discharge some 200 billion liters of raw sewage into natural waterways every year.

Bob Harrington lives in Galena Bay, B.C. His latest book, Testimony for Earth, and a new edition of The Soul Solution with a foreword by Dr. David Suzuki, are now available at www.hancockhouse.com.

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