Biological Treatment of Woodchip Biomass for use in Biorefineries

(De Gruyter) – Biorefineries offer us a chance to produce relatively low to zero environmental impact chemicals and fuels from waste products. Biowaste is collected from industries and then processesed to be used in a new product. The pulp and paper industry is transitioning to new products and market streams for additional revenues and enhanced competitiveness. Biorefineries in the pulp and paper industry normally generate liquor during the wood chip pre-hydrolysis step. However, many mills do not have an efficient means for disposal of pre-hydrolysis liquor resulting in their being burned as a fuel in an untreated state in a recovery boiler. Due to  pre-hydrolysis liquor’s low consistency this results in a high cost.

The authors aimed to analyze the biotreatability of the pre-hydrolysis liquor. Pre-hydrolysis liquor has had a diffcult time being converted in biorefineries as they possess a high chemical oxygen demand (COD), or the amount of oxygen consumed by a reaction in solution, and biochemical oxygen demand (BOD), which is the amount of dissolved oxygened needed by aerobic biological organisms to break down organic material in a solution over an amount of time.

The authors found that sequence batch bioreactors efficiently removed COD from mixtures of pulp mill effluent and pre-hydrolysis liquor. COD removal efficiency of 84 % was obtained for an 18 % pre-hydrolysis liquor 82 % effluent mixture that simulated a real dissolving pulp mill scenario. However, the treated effluent COD (1,422 mg l−1) was much higher than typical treated pulp mill effluent COD.

It was found that pretreatment of the pre-hydrolysis liquor by ultrafiltration proved to improve final effluent quality. The ultrafiltered product had a 72 % lower volume and higher organic solids content than untreated pre-hydrolysis liquor, meaning that sending it to the black liquor evaporation system would reduce energy consumption in the process.

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Edited for Content and Length by Dr. Matthew A. Hood.

The  full article can be found at De Gruyter in the Nordic Pulp & Paper Research Journal.

DOI: 10.1515/npprj-2018-3022

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