4.2.1 How much energy from biomass?
The yield of a crop (whether grown for food, fibre or fuel) is the mass of biomass produced per hectare per year and is the primary determinant of the energy we can obtain from that crop.
What factors do you think would contribute to variations in the yield of a crop?
Yields depend on several factors including:
- nature of the soil
- supplies of water
- choice of plant.
These variations mean that for energy crops the air-dry mass of plant matter produced annually on an area of one hectare can be as little as one dry tonne or as much as thirty dry tonnes. In energy terms, this represents a range from perhaps 15 GJ to 400 GJ per hectare per year.
How can this energy produced be extracted and turned into something useful? You’ll see in the next section.