The potential of Biomass and Bioenergy

Bioenergy has the potential to be a significant energy resource in Australia with ARENA estimating a potential of 371PJ each year from available resources. For Australia to contribute to the projected global outlook, we would need to experience a 40-fold expansion of the industry over 30 years. Such an expansion would be a significant challenge for industry and achieving it will require sustainable growth in feedstock resources, the application of modern technologies and the consistent development of new production facilities.

What is Biomass?

Biomass is plant or animal material that stores both chemical and solar energies. Biomass also contains a large amount of the element hydrogen, so it is an excellent source for hydrogen production and could provide further opportunities for farms in the future. The biomass available for bioenergy is dependent on a range of factors such as feedstock prices, proximity to markets, seasonal availability, and the relative value of biomass when converted to the energy in comparison to other commodities. See the Queensland governments biomass data tool aimed at helping local businesses get more value from organic material destined for landfill, disposal or other low-value uses.

What is Bioenergy?

Bioenergy is a form of renewable energy derived from (organic materials) and can be divided into two streams: biogas to generate electricity and heat, and fuels for transport and machinery.

Biogas - is produced from anaerobic digestion using waste effluents such as wastewater, sewage sludge and municipal solid waste. Using an airtight tank or covered lagoon, anaerobic bacteria (without oxygen) digest organic material in the absence of oxygen and produce biogas, composed principally of methane (CH₄) and CO_2. The methane can then be used to produce Hydrogen (syngas H2 and CO) in a process known as steam methane reforming which is the most common and cost-effective method for H2 production.

Biofuels - can be broadly grouped according to the conversion processes and are liquid fuels, produced by a chemical conversion process that results in the production of ethanol and biodiesel. Ethanol is produced by, and not limited to, sugar by-products, waste starch from grain, and biodiesel is produced from used cooking oils, tallow from abattoirs and oilseeds.

Extracting Energy

The most important parameter to characterise energy potential from a combustible material is the calorific value. This is defined as the amount of heat it produces when burnt, with excess of oxygen, to a given pressure and temperature. Three combustion conversion technologies used to convert biomass to energy include:

• Grate boilers - used for solid fuels, mainly for burning waste and biomass, but also for smaller coal furnaces.
• Fluidised bed combustion (gasification) - fuel particles are suspended in a hot, bubbling fluidity bed of ash and other particulate materials (sand, limestone) through which jets of air are blown to provide oxygen. These plants burn a variety of low-grade solid fuels, most types of coal, coal waste and woody biomass, at relatively high efficiency.
• Co-firing utility boiler - combusts any fuel and produces steam for the primary purpose of generating electricity.

The fuel type (heating value and moisture) and the conversion technology will influence the energy conversion efficiency. In the most efficient generation plant, around 30 per cent of the energy in biomass is converted to electricity and the rest is lost into the air and water.

Cogeneration, or combined heat and power plants, have greater conversion efficiencies because they produce both electricity and heat. For example, the energy conversion efficiency for wood waste in a direct combustion facility is about 35 per cent, compared to between 70-85 per cent efficiency in a combined heat and power facility. Further, process waste heat can be usefully applied for heating in winter and, via an absorption chiller or refrigeration, for cooling in summer. The sugarcane industry generates over a quarter of Queensland’s renewable energy meeting more than 2 per cent of Australia’s large scale renewable energy target. The sugar mill directly consumes the heat and electricity generated and any surplus steam is used to generate electricity and feeds back into the power grid. A great case study showing the potential energy savings from a cogeneration plant and the production of biogas at a feedlot can be viewed here.

The use of gasification is more efficient for energy recovery in terms of electricity generation than traditional combustion. In gasification, solid biomass is heated to high temperatures (800–1000°C) in a gasifier and converted to syngas primarily composed of Hydrogen, Carbon monoxide, Carbon dioxide, water vapour and Methane. One benefit is that there are lower amounts of Sodium oxide, Nitrous oxide, and dioxin emissions than in a traditional combustion process.

In addition, Biochar can be produced from heating organic material like crop waste, grass, woodchips, and manure in a high temperature low oxygen process known as pyrolysis. Biochar is a stable, carbon–rich form of charcoal that can be applied to soil. Research shows that biochar derived from grasses or crops appears to have the best balance of agricultural benefit and carbon stability. It can improve soil fertility and productivity by increasing water holding capacity from increased carbon content in the soil and has been shown to raise wheat germination. Overall biochar can help to reduce greenhouse gas emissions and mitigate against future climate change and by applying it to soils could create carbon offsets.

Policy Issues:

Food versus fuel.

Bioenergy should not diminish the food available to growing populations and a balance of resources is needed. Ideally, the feedstock would be a by-product or land required for feedstock production will not compete with other demands for productive land. There is however potential to expand Australia’s bioenergy sector utilising more of these organic and waste products. A key step towards improving the sustainability of production and achieving greater energy density without greater energy use – is through technological advancements and improvements in conversation efficiencies. Advances in technologies will increase the range of resources and might include non-edible (woody) parts of plants along with the production of algae using bioreactors.

Carbon Neutral

An International Energy Agency report, notes that bioenergy from woody biomass can be considered carbon neutral because the carbon that is released during combustion has previously been sequestered from the atmosphere and will be sequestered again as the plants regrow. However, the full supply chain must be considered, and all emissions associated with the production, processing, transport and use of bioenergy need to be included.

Queensland

The Queensland Government has been actively supporting the bioenergy sector, with the updated Queensland Biofutures 10-Year Roadmap and Action Plan launched in 2022, providing a refreshed vision and further funding opportunities for the industry. As of 2021, bioelectricity generated from bagasse (sugar cane), wood waste, and gas from landfill and sewage facilities, only accounted for 1.3% Australia’s electricity generation. The big news is the planned expansion of the biofuels industry and new markets should open as more bioethanol refineries come on-line.

There is increasing use and interest in bioenergy on both a small and large scale from industry, like that of the Bundaberg BioHub, and farms as they begin to utilise onsite waste streams to become more energy resilient and to meet net zero targets. Although bioenergy offers a potential renewable form of energy, good management of resources is required to minimise potential land degradation and resource use. Additional risks to consider include drought, flood, fires, climate change and energy prices.

The right economic conditions may encourage growers to diversify towards bioenergy production or upgrade infrastructure to produce energy onsite and offset consumption. Explore current funding opportunities here.