When we use plants, animals and their by-products to generate energy we call it bioenergy.
What is bioenergy?
Plants capture solar energy through photosynthesis and use it to grow biomass. When we use biomass to generate energy we call it bioenergy. This means that bioenergy is a form of renewable energy.
Bioenergy and greenhouse gas emissions
The use of biomass to produce bioenergy releases carbon dioxide (CO2) into the air. This is offset by new plant growth so that the total emissions are zero. The international climate change agreements recognise bioenergy as a carbon neutral fuel because of this process. By replacing fossil fuels in energy generation, bioenergy also saves carbon emissions.
Total life cycle emissions
Additional emissions occur in the cultivation, harvesting, refining and transport of bioenergy. EU and other countries legislation and guidelines take total life cycle emissions into account. An example is the EU directive on renewable energy. This requires biofuel emissions to be 60% less than those of the petrol and diesel fuels it is replacing by 2018.
Biomass comes from living or recently living organic material. The primary source is plant material such as trees, crops and grass. Animals that directly or indirectly consume plants are also considered as biomass.
Agricultural waste and residues
These are the leftovers from farming and food production. This category includes materials like animal manures and straws from cereal crops.
These are the low value parts of trees that arise as part of the forest care or are collected after forests are cut down.
Dedicated energy crops
Crops like wheat and oil seed rape are grown to produce biofuels. Willow and miscanthsus are burned to produce heat and electricity. Grass silage can be used to produce biogas in anaerobic digestion systems.
By-products and wastes
- Sawdust, and other wood industry by-products, are common bioenergy fuels
- Food waste and other organic waste is used to fuel biogas and electricity production
- Used cooking oil is a valuable feedstock for biofuel production
Turning biomass into energy
Biomass fuel has to undergo processing before energy generation is possible. Bioenergy supply chains include: growing, harvesting, refining, transportation, storage and energy conversion.
Wood chips and pellets, biogas and biomethane, biodiesel and bioethanol, are examples of refined solid, gas and liquid fuels. Refining can aim to:
- Reduce the amount of water held in the raw resource
- Compress more energy into a product
- Remove the parts that have no energy value
- Improve the consistency of the fuel
Burning solid biomass fuel releases energy that can heat homes and businesses. It also can make steam for input to industrial processes and to drive electricity generators. Cars, trucks and other vehicles use liquid biofuels. Gas turbines, boilers and compressed gas vehicles can all use biogas as a fuel.
Biomass uses and products
Biomass can provide energy to move our cars, trucks, buses, ships and planes. It can supply fuel to heat our homes, businesses, and industry, and power our electricity grid. Modern processes use many different types of biomass to produce several products.
The burning of solid biomass for heat and power remains the most common use of biomass worldwide. Wood refineries produce wood pellets, chips and other types of solid fuel.
Biofuel refineries produce liquid fuels often used for transport. Biofuels made from food crops are called 1st generation biofuels. In a bid to enhance biofuel sustainability governments are incentivising use of 2nd generation materials that do not compete with food production.
Biogas and biomethane
Anaerobic digestion and other renewable gas facilities produce biogas. Biogas can be upgraded to biomethane and put into the gas grid. Both biogas and biomethane have potential as heat, transport and electricity generation fuels.
Bioenergy in Ireland
Approximately 3.5% of the energy we use in Ireland comes from Irish grown biomass. There is a lot of potential for this to increase. By 2035, the bioenergy potential is close to 30% of 2015 energy demand.
- Forestry has the largest potential to expand at current market prices for energy
- Energy crops have the largest potential to expand at higher market prices
- Agricultural and other wastes are often available at low or even negative costs
Irish bioenergy sites
Biofuel refineries must be quite large to achieve economies of scale. For this reason they are rare in Ireland. The Irish market for biofuels and the availability of biomass resource has had limited development.
Wood processing sites are common in Ireland. These supply firewood, wood chips and wood pellets. Several anaerobic digestion sites are in operation. Some farms and several water treatment facilities are producing biogas. Several sites have plans to inject biomethane to the gas grid.
View bioenergy sites in Ireland on the IRBEA (bioenergy industry body) website.
Future technologies and bioenergy research
The development of bioenergy technology is an active research area.
- Technologies such as gasification and pyrolysis can introduce large amounts of renewable onto the gas grid. Some also hold the promise of wider energy system benefits.
- Power to gas technology uses electricity as part of the process of making renewable gas. This can generate large amounts of renewable gas and balance the electricity grid.
- Research into advanced biofuels for the jet engines of airplanes offers a much needed option to reduce emissions in aviation.
SEAI represent Ireland on an international research collaboration for bioenergy. This allows Irish researchers to participate in worldwide research efforts. Our research section has information on SEAI’s research activities.