A horizontal drum kiln is a traditional method widely used in Southeast Asian countries for producing biochar. An understanding of temperature conditions in the kiln and its influence on biochar properties is crucial for identifying suitable biochar applications. In this study, four agricultural residues (corncob, coconut husk, coconut shell, and rice straw) were used for drum kiln biochar production. The agricultural residues were turned into biochar within 100–200 min, depending on their structures. The suitability of biochar for briquette fuels was analyzed using proximate, ultimate, and elemental analysis. The biochar’s physical and chemical properties were characterized via bulk density, iodine number, pHpzc, SEM, and FTIR measurements. All biochars had low O/C and H/C ratios and negative charge from both carbonyl and hydroxyl groups. Coconut husk and shell biochar had desirable properties such as high heating value and a high amount of surface functional groups which can interact with nutrients in soil. These biochars are thus suitable for use for a variety of purposes including as biofuels, adsorbents, and as soil amendments.

In this work, we evaluated the valorisation of agricultural waste materials by transforming coconut husks and shells, corncobs and rice straw into biochar for water treatment in aquaculture. We compared the biochars’ suitability for removal of organic micropollutants (acetaminophen, oxytetracycline, tetracycline, enrofloxacin, atrazine, diuron and diclofenac) from surface water needed for aquaculture. The biochars were prepared by three methods ranging from inexpensive drum kilns (200 °C) to pyrolysis with biogasfication (350–750 °C). Overall, antibiotics tetracycline and enrofloxacin were the most strongly sorbed micropollutants, and coconut husk biochar prepared at 750 °C was the best sorbent material. Molecular Dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions and there is a possibility of multilayer sorption for some of the micropollutants. We observed, a strong impact of ionic strength (salinity), which is an important consideration in coastal aquaculture applications. High salinity decreased the sorption for antibiotics oxytetracycline, tetracycline and enrofloxacin but increased diclofenac, atrazine and diuron sorption. We considered coconut husk biochar produced in drum kilns the most practical option for biochar applications in small-scale coastal aquacultures in South Asia. Pilot trials of canal water filtration at an aquaculture farm revealed that micropollutant sorption by coconut husk biochar under real-world conditions might be 10–500 times less than observed in the laboratory studies. Even so, biochar amendment of sand enhanced the micropollutant retention, which may facilitate subsequent biodegradation and improve the quality of brackish surface water used for food production in coastal aquaculture.

An Analytic Network Process (ANP) modeling for a decision support system was proposed to identify suitable options for biomass energy plants using rice husk in rural areas of Thailand. In this attempt, direct combustion and gasifi cation systems for a biomass energy plant were evaluated. An ANP-based model was used to consider criteria, sub-criteria, and alternatives. Environmental and social problems were considered to construct the model. The ANP modeling used multiple criteria analysis and specifi c alternatives to clarify discussion points in decision making. The study area was selected based on the maximum availability of rice husk in the Suphanburi and Nakhonsawan provinces of Thailand. Prior to the fi eld survey, a focus group discussion and later a structured questionnaire were used to interview the respondents in the provinces. The ANP model was infl uenced by the policy for developing rural area support in Thailand. For criteria priorities, benefi ts-criterion and risks-criterion had the highest priorities. The ANP model results showed that the gasifi cation system was likely a better alternative than the direct combustion system in a cooperative scenario considering environmental and social concerns. In contrast, direct combustion was likely a suitable energy plant in an industrial scenario considering the benefi ts and economic issues.

Evaluation functions for minimizing the disparity between energy supply and demand and reducing the fi eld area for biomass production, which are based on energy benefi ts, were proposed in a system design for biofuel production. An Exergy Profi t Ratio (ExPR) and an extended the Energy Profi t Ratio (EPR) were also proposed to measure the quality and availability of energy for the biofuel plant in Utsunomiya City in Tochigi Prefecture, Japan. In the calculation of minimum fi eld area of biomass production based on societal demand in household of Utsunomiya City, 17,500 ha was the minimum value by the evaluation function by energy (E ( ( system E ) and 29,500 ha was the minimum value by the evaluation function by exergy (E ( ( system E EX ) under the case of lighting: 100% electricity; heating: 89% electricity and 11% of vapor. On the other hand, 17,000 ha was the minimum value by E system E and 29,000 ha was the minimum value by E system E EX under the case of lighting: 100% electricity; heating: 100% electricity and 100% of vapor. Thus, if EPR and E system E of bio-ethanol & electricity production were underestimated for a minimum fi eld area, then ExPR and E system E EX could be used to maintain the results of introducing biofuel production to prevent fi eld area shortages for biofuel production.