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Many studies identified the optimum temperature to maximise bio-oil/biochar yield using fast pyrolysis from woody biomass. However, the optimum mix of biochar and bio-oil production and their final utilisation to achieve optimal environmental and economic benefits are yet to be investigated. Hence, the aim of this study was to identify the optimum mix and utilisation using life cycle assessment and costing approach. Two utilisation scenarios were analysed: Scenario 1 considered terrestrial carbon sequestration through spreading biochar in corn fields while Scenario 2 assumed the co-combustion of biochar to displace coal in a coal-fired power station. In both scenarios, bio-oil was assumed to substitute heavy fuel oil in an industrial boiler. The functional unit used in the study was 1 Mg of green thinned logs from hardwood plantations. Scenario 1 showed outstanding greenhouse gas emissions offset (1,680 kg-CO 2-eq per function unit). However, this scenario lagged behind when considering other environmental impacts. Scenario 2 delivered more modest greenhouse gas offset, but it had better overall environmental and economic performance. The results indicated that the overall environmental performance of Scenario 2 decreased with increasing pyrolysis temperature due to the decline in biochar yield as well as the increased energy consumption during the pyrolysis process. Meanwhile, lifecycle cost reduced when the pyrolysis temperature increased because of the increased bio-oil production, which has higher economic value than biochar. Assuming equal weights for the environmental and economic functions, the optimal performance of Scenario 2 is likely to be achieved when the pyrolysis process is run at 500 ˚C with the bio-oil and biochar yields being 64% and 22%, respectively. Monte Carlo Analysis revealed that for balanced environmental and economic weights (30%-70%) the solution is robust. The Monte Carlo Analysis results suggested that under the optimal conditions, there is 97.5% likelihood that Scenario 2 would achieve 1,050 kg-CO 2-eq greenhouse gas emissions offset and realise $25.8 life cycle cost savings per functional unit. This study demonstrates an easy method to incorporate life cycle assessment and costing into an optimisation decision making framework. Thus, allowing a more comprehensive assessment of policies incorporating multiple environmental impacts (criteria). It contributes to the debate about the economic and environmental validity of using forestry by-products, as well as other low cost woody biomass as a renewable energy source.

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Based on the principle of self-coagulation of microorganisms, the flocculant-producing denitrifying bacterial TN-14 sludge was added to the continuous-flow reactor for treating domestic sewage. The bacterial TN-14 sludge acted as the main seed sludge to promote the rapid formation of aerobic granular sludge. The sludge morphology, sludge volume index (SVI) values, amounts of extracellular polymeric substances (EPS), and the role of calcium in the granulation process of the sludge were investigated. Results showed that brown aerobic granules with the particle size of 0.5 ~ 2.0 mm was successfully cultivated at 40 days, and its SVI decreased from 122.62 mL g initially to 46.61 mL g and remained at 44.28 ~ 60.51 mL g afterwards. The protein (PN) content in sludge EPS increased from 76.4 mg g initially to 512.3 mg g. Compared with PN, the polysaccharide (PS) content did not change much throughout the operation process of the bioreactor. Energy-dispersive spectrum (EDS) showed that Ca elements were deposited inside the granular sludge, and X-ray diffraction (XRD) showed that Ca elements existed in the granular sludge in the forms of CaCO, KCaPO, CaPO, and CaO(PO). The formation mechanism of continuous-flow aerobic granular sludge was that bacterial TN-14 sludge could promote the EPS content of sludge, and PN content of EPS increases the hydrophobicity and settling performance of the sludge. Calcium mainly exists in the granular sludge in the form of inorganic calcium phosphate, and therefore plays the role of nucleation in sludge granulation.