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Low-quality biomass transformed

An EU-funded initiative has developed a process for treating low-value biomass to remove the ash content and provide high quality feedstocks.


Bioenergy accounts for over 61 % of all renewable energy consumed in Europe. The biomass industry is aiming to meet this high demand by making better use of feedstocks and waste. At present, this waste is barely exploited in terms of energy, because of its high ash content, which is carefully regulated under ISO 17225, an international standard. The EU-funded Horizon 2020 BIAR project addressed this challenge, developing a chemical process for removing ash content from ash-rich lignocellulosic material like bark and rice husks. “The BiAR process acts as a form of pre-treatment with a very wide range of possible applications, splitting the organic and inorganic constituents of biomass,” says project coordinator Gian Claudio Faussone. New feedstocks exploited Biomass comprises cellulose, hemicellulose and lignin. There are three differentiated steps to the process. The first uses a solvent and catalyst at moderate temperature (200 °C) and pressure, in a reaction known as solvolysis, to break down biomass into smaller organic elements and compounds. The second phase employs mechanical filtration at high pressure to remove the larger inorganic compounds from the dissolved biomass. In the final phase, the filtrate is distilled to recover the solvent, which is used again in the process. The remainder of the distillate contains pure ash-free organic matter, which is chemically identical to the original biomass material, minus the ash. To date, only good quality feedstocks are used for pellet production. However, Faussone claims, “With BiAR, residual biomass that are not currently exploited like rice husks which contain 16 % ash, or even sludge digestate that has up to 40 % ash can be useful and safe.” Sludge, for example, is contaminated by heavy metals, hence it can only be burnt in dedicated incinerators fitted with sophisticated environmental protection devices. “With BiAR, heavy metals are pulled out of sludge, which can then be safely burned in any traditional stove,” Faussone explains. Multiple applications By providing new sources of available biomasses, the specific cost of bio-based energy can be reduced. Furthermore, using already available but currently unexploited feedstocks will help reduce CO2 emissions. According to Faussone: “Our targeted market segment is business-to-business, like biomass power plants, district heating, wastewater treatment plants, and wholesale pellets distributors who would benefit from BIAR application.” The most interesting aspect of BiAR is the potential application of the organic fraction. Normally residual biomasses have an ash content that is too high for use in other applications. In addition, the inorganic fraction of the ash is too high, which make these biomasses useless. “Using the BiAR process we can obtain the organic fraction, ash free; and the inorganic fraction, organic free, thereby, overcoming the normal limitations,” comments Faussone. The BiAR process has many possible applications from large scale pellet production to sludge treatment and from specific ash recovery to laboratory experiments for investigating the properties of pure biomass. Faussone concludes: “Ash free from organics can have very interesting uses, for example for electric battery manufacture, the potential for which we will study in the future.”


BIAR, biomass, ash, organic, feedstock, sludge, inorganic, rice husk, pellet, waste, solvolysis

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8 June 2020