Elucidating the role of sub-thermophilic temperature and pre-hydrolyzation for effective upgrading scheme of old swine manure digesters.

Solids concentration, temperature, and digester configuration were subjected to biomethanation study to identify effective retrofitting schemes for old swine waste digesters. Batch assays were commenced to determine an appropriate scenario at 30-55 °C and total solids 1-3 %TS. Sub-thermophilic temperature (45 °C) was found desirable with an additional 11.1 % methane yield, while digestion at higher TS induced ammonium inhibition. Subsequent batch experiments lasted 72 hrs for hydrolytic-acidogenic assessment under various temperatures. Heating control at 45 °C and 55 °C for 24 hrs increased hydrolysis efficiency 4.6-5.7 folds above control but showed no significant difference (α = 0.05) between them. Limited heat supply from biogas engine dictated the continuous digestion study to operate pre-hydrolysis reactor at maximum temperature of 45 °C. The two-stage strategy demonstrated best overall performances at the sub-thermphilic combination, raising methane yield by 35.4 %. Next-Generation Sequencing indicated remarkable shifts in abundance and diversity, especially for hydrolytic organisms, which expanded from 54 to 70.2 % by sub-thermophilic temperature.

Investigating fouling deposition during combustion of hydrothermally treated palm empty fruit Bunch: Pilot-Scale study for industrial hydrothermal reactor.

Inorganic elements in palm empty fruit bunch (EFB) are problematic in boiler operation, causing slagging and fouling deposits. The first pilot-scale hydrothermal treatment (HTT) system was commenced in a palm oil mill to remove undesirable elements. Fuel properties, combustion behavior, and fouling deposition of HTT-EFB were investigated. Liquid temperatures and treatment times in the HTT system significantly altered EFB-fuel properties. At ≥ 60 °C, potassium removals of at least 78 % were achieved, generating EFB-fuel containing potassium below 0.5 %wt. Later, a series of EFB combustion experiments were conducted in a specially designed fixed-bed reactor to simulate the tube surface of industrial boilers. Fouling deposition from HTT-EFB combustion reduced to below half of untreated EFB at all HTT conditions and combustion temperatures studied. The deposit-to-fuel ratio of HTT-EFB combusted at 1,000 °C was 37.3 % lower than untreated EFB combusted at a typical EFB boiler at 800 °C. Results demonstrated great potential for HTT-EFB in industrial applications.

Key fuel characteristics and techno-economic aspects of torrefied rubberwood biomass pellets produced by incorporating various cassava-based binders at varied doses.

Improving energy content and hydrophobic nature of woody biomass can be pursued through torrefaction. This gives torrefied biomass with a low bulk density, potentially increasing storage and transport costs. To overcome this issue, densifying the torrefied biomass is necessary. However, poor binding of particles makes densification challenging without using a binder. Therefore, the aim of this study was to investigate the physicochemical characteristics and techno-economic aspects of torrefied rubberwood biomass (TRWB) when pelletized using various cassava-based binders at different blending ratios. The selected binders included cassava starch (CS), cassava pulp (CP), and cassava chip (CC). Each binder at 5%, 10%, or 15% (wt.) was mixed with TRWB and water before pelletizing using a flat die machine. The results revealed that pelletizing TRWB with different cassava-based binders at various blending ratios influenced the physicochemical characteristics of the TRWB pellets, particularly dimensions, bulk density, fuel and atomic ratios, and energy content. The TRWB pellets demonstrated energy densities in the range of 7.95-11.39 GJ/m3, and their mechanical durability and fine content fell within acceptable ranges. The TRWB pellets maintained their shape during 120 min of water soaking, with water absorption levels varying by binder dose. The pelletizing ability, material, and energy costs of TRWB pellets depend on binder type and dose. CP can be applied as a binder for pelletizing torrefied rubberwood biomass. However, the mechanical durability of the product needs to be above the user requirement or standard.

Bioaugmentation of latex rubber sheet wastewater treatment with stimulated indigenous purple nonsulfur bacteria by fermented pineapple extract

Background Treating latex rubber sheet wastewater often leads to the generation of a rotten-egg odor from toxic H2S. To increase the treatment efficiency and eliminate H2S, purple nonsulfur bacteria (PNSB), prepared by supplementing non-sterile rubber sheet wastewater (RAW) with fermented pineapple extract (FPE), were used to treat this wastewater under microaerobic light conditions. The following 3 independent variables: chemical oxygen demand (COD), initial pH and FPE dose were investigated using the Box-Behnken design to find optimal conditions for stimulating the growth of indigenous PNSB (PNSBsi). Results The addition of 2.0% FPE into RAW, which had a COD of 2000 mg L- 1 and an initial pH of 7.0, significantly decreased oxidation reduction potential (ORP) value and stimulated PNSBsi to reach a maximum of 7.8 log cfu mL- 1 within 2 d. Consequently, these PNSBsi, used as inoculants, were investigated for their ability to treat the wastewater under microaerobic light conditions. A central composite design was used to determine the optimal conditions for the wastewater treatment. These proved to be 7% PNSBsi, 0.8% FPE and 4 d retention time and this combination resulted in a reduction of 91% for COD, 75% for suspended solids, 61% for total sulfide while H2S was not detected. Results of abiotic control and treatment sets indicated that H2S was produced by heterotrophic bacteria and it was then effectively deactivated by PNSBsi. Conclusions The stimulation of PNSB growth by FPE under light condition was to lower ORP, and PNSBsi proved to be effective for treating the wastewater.