Bioenergy is an important form of renewable energy that is stored in biological material like wood, wood waste, manure, straw, and other by-products of agricultural processes. Bioenergy in these sources can be converted and used to generate heat or electricity, or to produce transport fuel.
Using stored energy from the sun
The source of bioenergy is organic material - this is sometimes referred to as biomass. Biomass is effectively a store of solar energy, where energy from the sun is captured through photosynthesis and stored as the plant or tree grows.
Bioenergy can be derived from trees and crops grown specifically for their energy content but also indirect sources of biomass derived from waste products from industrial, commercial, agricultural, and domestic activities. These wastes include straw, animal manure, animal fat, and municipal solid waste.
Wood has been used by humans as a source of energy for thousands of years, in the form of fires for heat and light.
Wood, including wood residue and by-products, and dedicated, fast growing trees, bushes and shrubs, is being increasingly recognised as a valuable source of energy for larger-scale commercial and industrial applications.
Wood energy can be used to generate heat and electricity, and can also be converted into liquid fuels similar to petrol and diesel. When used as a substitute for fossil fuels (coal, oil, and gas), wood reduces the amount of greenhouse gas emissions produced by New Zealand.
Burning wood has almost zero net greenhouse effect as long as the carbon dioxide given off during combustion is absorbed by the growth of the next crop of trees or shrubs.
Using wood energy can also be very cost effective, particularly when the wood residue being used is a by-product of an existing process. It can often be used to provide some of the energy for the production process itself.
Wood energy use in New Zealand
Wood energy provides about five per cent of New Zealand's total energy supply. Wood energy is mainly used by the timber industry, which burns residue wood to provide heat energy. Residential wood burners and open fires account for over 20% of wood energy in New Zealand.
There are opportunities to significantly increase our use of wood as an energy source. EECA is administering the Wood Energy Grant Scheme (WEGS) which aims to increase the use of wood residues as an energy source for industrial use.
More about using wood in industry and business
More about using wood for home heating
Biogas is a gas produced during the breakdown of biological matter which can be used to provide energy. Biogas can be produced using dairy effluent on farms, at sewage plants, or at landfill sites. The potential for energy from biogas using existing sources of biological waste is enough for more than 30,000 homes for a year.
At landfill sites, biogas is generated by wet biological material decomposing in the right conditions. The landfill can be covered to prevent the gas from escaping into the atmosphere. It is then captured and can be used in a gas turbine to generate electricity, or used directly as a heat source.
Biogas also has particular potential on farms where the animal effluent can be used to generate energy. The resulting sludge can then be used as a fertiliser as any harmful bacteria will have been killed during the biogas production process.
At some sewage treatment plants, biogas can also be produced, captured, and utilised. This process can have the additional benefit of reducing waste to landfill or incineration.
Biogas contains methane, which has 20 times more greenhouse gas effect than carbon dioxide. The process of burning biogas for electricity generation or heat converts the methane into carbon dioxide, therefore significantly reducing the environmental impact.
Biofuels are fuels that can be produced from renewable materials, such as plants. They are usually blended with petrol and diesel to make biofuel blends. The most common biofuels are bioethanol, which is blended with petrol; and biodiesel, which is blended with diesel.
Sustainably-produced biofuels have many benefits. By using a renewable alternative to fossil fuels to run our cars we can:
- Reduce greenhouse gas emissions which contribute to climate change
- Improve air quality by reducing air pollution
Lessen our dependence on imported oil
Biofuels in New Zealand
Liquid biofuels are used as a full or part-substitute for oil products, mainly in the transport sector. Biofuel blends have been available in some parts of New Zealand since August 2007.
Presently, the biofuels sold in New Zealand are from the following sustainable sources:
- Bioethanol from whey, a natural by-product of the New Zealand dairy industry
- Bioethanol from Brazilian sugarcane, grown in the south of Brazil. Brazilian sugarcane bioethanol is one of the most sustainable biofuels available (Download a report about the sustainability of Brazilian bioethanol and on labour issues connected to production.)
Biodiesel, from used cooking oil and rapeseed grown as a break crop. (Sustainability reports on these sources can be found in More information below)
Future sources of biofuels
Internationally and in New Zealand a lot of work is underway on the development of second generation biofuels (biofuels produced from wood, straw, wastes etc).
Bioethanol and synthetic renewable petrol or diesel can be produced from wood residue but the processess are not yet commercialised.
While first generation biofuels (produced from crops, agriculture) have an important role in renewable transport fuel development, it is the second generation biofuels that are being viewed as the way forward in the long term, with some ground-breaking work already well underway.
The forestry Crown Research Institute Scion has recently investigated bioenergy options for New Zealand. Its research shows how New Zealand could be self sufficient in transport fuels made from purpose grown forestry on marginal land - for example, land currently used for low intensity, low return sheep grazing.
- Using biofuels
- EECA's biofuels programme
- EECA's renewable transport programme
- Sustainability report - tallow
- Sustainability report - rapeseed
- Bioenergy in business
- Using wood in industry and business
- Using wood for home heating
- Wood Energy Grant Scheme (WEGS)
- Bioenergy Knowledge Centre
- Bioenergy Association of New Zealand (BANZ)