Pacific Pyrolysis (PacPyro) has been offered $4.5 million by the Victorian Government to pilot a commercial-scale production facility in Melbourne. The project will demonstrate PacPyro’s proprietary technology’s ability to deliver a solution for urban green and wood waste by converting it into renewable electricity and biochar.

The process

Slow-pyrolysis is the heating up of biomass (also known as ‘organic material’) in the absence of oxygen so that it thermally decomposes, without burning. The volatile components of the biomass are given off and this combustible gas stream – ‘syngas’– is then cleaned up to a quality that can be utilised in gas engine generators for electricity production, or in many thermal energy applications such as dryers or boilers.

PacPyro, in developing its technology, has steered away from condensing any bio-oil product from the process as it believes that safe and sustainable markets for bio-oil still require significant research and development. The PacPyro kiln is therefore optimised for minimal production of bio-oils, and any bio-oils that are produced are cracked down into more syngas in the proprietary gas-cleaning arrangement.

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The solid remaining after the de-volatilisation of the biomass is called ‘char’. The processing results in a dense carbon structure of conjugated aromatic rings, which has a highly developed surface area. When this char product is utilised as a soil amendment it is referred to as biochar. The greenhouse gas balances across slow-pyrolysis projects have garnered a lot of interest because they have the potential to be carbon negative, that is, to remove carbon from the atmosphere. Plants have evolved over millions of years to efficiently take up CO2 from the atmosphere. When plants die, however, they decompose, releasing the carbon stored in the biomass back into the atmosphere. Under some conditions, such as in landfills, a portion of the carbon in the biomass can be released as the potent greenhouse gas, methane. However, if biomass is directed into a slow-pyrolysis process, about half of the carbon stored will be made into syngas.

When syngas is combusted for energy the carbon is released as CO2 back into the atmosphere, with this energy providing a renewable alternative to fossil fuels. The other half of the carbon is stabilised in the biochar. Biochar has been shown to be very recalcitrant in soils, as it is not susceptible to degradation in the environment by biological (soil microbes) or chemical pathways. Therefore, across the life of the project, more carbon is taken up by the plants than is released back into the atmosphere – hence a net removal is achieved.

The biochar rollout

Biochar’s application as a climate mitigation strategy could be rolled out relatively quickly, as a significant amount of existing infrastructure already exists for both biomass collection and handling (waste management, agriculture and forestry), and soil amendment use.

Project developers such as PacPyro are actively working with government to ensure that the carbon mitigation benefits of the technology are recognised under the Carbon Farming Initiative and other emissions reduction schemes in future. There is a common interest to ensure that verifiable and scientifically robust greenhouse gas accounting methodologies are applied so that projects can ultimately gain an additional revenue stream from carbon offsets to help get established.

Securing sustainable biomass

The large-scale rollout of the bioenergy technology will require biomass supply. Project developers in the bioenergy field need to focus on sustainable biomass sources as the cornerstone of the emerging industry. Slow-pyrolysis technology offers the opportunity to avoid the food-versus-food debate and add value to a large range of waste and low-grade biomass feedstocks which may otherwise be destined for landfill.

The PacPyro pilot plant located at Somersby in New South Wales, for example, has been successfully operated since 2006 on many such materials, including municipal greenwaste mixed with biosolids (waste water treatment sludges), paper mill residues (paper fibre sludges, bark and wood), feedlot manures, poultry litter and crop residues. The existing pilot facility, which is approximately one tenth of the scale of the commercial plant planned for Melbourne and established with grant assistance by the NSW State Government, has been instrumental in enabling biochar research.

At both the 3rd International Biochar Conference held in Rio de Janeiro in 2010, and the 2nd Asia Pacific Biochar Conference is Kyoto in 2011, Australian researchers were a strong contingent, presenting a large volume of world-leading research. The NSW Department of Primary Industries, for example, established their first biochar field trial plots in 2006 and have since made a large commitment to contributing to this research field.