Updating the story so far, the Pyramid Farms’ greenhouse operation consumes about 28,000 tonnes of wood waste per year, but this is a short-term solution to fuel challenges (i.e., changing supply and demand). Tree species (willow, poplar) do not provide the heat output or growth compared to miscanthus. At current Ontario prices, Dean suggested that:
- Fossil fuels cost about $10-11/GJ.
- Waste wood is about $3/GJ but likely to rise.
- Gas is $5.85/GJ.
- Miscanthus costs about $5.25/GJ.
Planted as rhizomes, the crop produces about eight to 10 tonnes/acre dry matter by the third year. At about $60/tonne delivered (providing about 16-17 GJ/tonne), total inputs mean energy costs are about $5-$5.50/GJ. However, as a perennial, miscanthus yields value for maybe 20 years, with almost no further inputs. Tiessen estimates returns for contract farmers will be about $400/acre delivered.
Miscanthus “can be processed into a range of forms from conventional bales … to compacted forms for different energy end users and uses, and be utilized to produce heat, electricity, liquid fuels (bio-ethanol), industrial materials (bio-composites) and agricultural markets.”1 Further, it can be turned into grow bags for as cheap as 21 cents/slab. It has also been extensively tested for packaging and even building applications.2
Changing land use from food to fuel production is a contentious issue, but Tiessen has his arguments prepared (see New Energy’s website discussion on the U.S. Advanced Energy Initiative1). A recent (U.S.) government-funded study concluded 1.3 billion tonnes of biomass could be produced annually, with one billion tonnes coming from agricultural production without negatively affecting food, feed or export potential. This represents approximately 10 per cent of current farmed area, comparable with wheat.”1 (Remember, though, that miscanthus has many more applications than “just” fuel.)
Growers are always inventive and are finding other ways to generate (and use) biomass. British grower Philip Pearson will soon be operating “carbon negative” trucks run on “eco-fuel” (bio-methane) made from waste leaves and fruit from his tomato crop in an anaerobic digestion system he built a couple of years ago. His first vehicle should be up and running by next summer. “We have made the fuel – we are just making sure that it is of a consistent quality.” All of the greenhouse waste material is fed into the digester, thereby also reducing the company’s annual landfill volumes from 2,500 tonnes of four years ago to 200 tonnes in 2009.3 Ingeniously, Pearson’s system produces a liquid digestate (rather than sludge) and “he has made a deal with the U.K. Sports Turf Research Institute, which, from next year will enable its associations to use the whitish-green liquid as a fertiliser.”3
Since 2007, a U.K. supermarket has been powered entirely by electricity generated as a byproduct from a cogen system used to heat local tomato greenhouses. Now, one of the greenhouse companies has built an anaerobic digester to provide some of the fuel, and like Pearson’s system, recycles waste from the greenhouse tomatoes and other fruit and vegetable waste, turning it into methane.4
1 Visit New Energy’s website at: www.newenergyfarms.com.
2 Cantus Biopower Ltd, at www.cantusbiopower.com.
3 “Anaerobic digestion fuel may run vehicles”, Horticulture Week (Oct. 15, 2010)
4 “Innovations by tomato growers help…”, Horticulture Week (Oct. 22, 2010)