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Biological wood oxidation (BWO) offers great potential for sustainable heat generation, and our previous work has shown that nutrient addition (especially nitrogen; N) is necessary for fast BWO. To reduce the cost and environmental impacts of chemical nutrients, human urine was chosen as a source of nutrient in this study. We investigated the factors including urine dilution ratio, the types of urine (fresh urine and synthetic urine), and urine readdition, by studying their effects on oxygen consumption and dry weight loss of the wood. After 42-day incubation, synthetic urine with five times dilution (corresponding to 1.2 ‰ N dry basis of wood) showed the best performance; it improved the oxygen consumption by 3.8 times and wood weight loss by 3.3 times than that without urine addition (analysis of variance (ANOVA), P < 0.05). At the same N level, fresh urine addition was able to enhance the BWO more efficiently than synthetic urine addition, further improving the oxygen consumption by 64% and weight loss by 47% (ANOVA, P < 0.05). During the BWO process, the decrease in wood degradation rate was possibly due to the decrease in nutrient availability. With the readdition of synthetic urine, the total oxygen consumption and weight loss after 100-day incubation increased by more than 40% compared with the group without readdition. However, readdition of only N-containing components did not increase the BWO, showing that elements (other than N) were important. To this end, we demonstrated the feasibility of human urine as a waste-based nutrient source for fast BWO and the possibility of long-term BWO operation via urine readdition.

Biological wood oxidation (BWO) is proposed as a cleaner alternative to wood combustion for heat production and wood waste management. Currently, BWO is not extensively studied and little is known about it. Nevertheless, given the composition of wood residues, which is dominated by carbon, nutrient availability may become a limiting factor during BWO. Our objective was to study the nutrition requirements for sustaining the BWO. For this purpose, three different factors including nitrogen addition, phosphorus addition and pH, were studied. Oxygen consumption and mass loss were monitored and used to evaluate the impact of nutrition on BWO and to calculate the theoretical heat production. The result showed that nitrogen addition at a relatively low level (2.5-10 mg/g) enhanced the cumulative oxygen consumption by 60–124% and mass loss by 28–95%, when compared with the BWO without nitrogen addition. The highest nitrogen addition examined in this research (20 mg/g), on the other hand, did not enhance BWO. Different phosphorus addition (0.5–5 mg/g) and pH (4–6) had little impacts on BWO. The highest theoretical heat production rate (0.63 W/kg dry wood biomass) was achieved using 2.5 mg/g nitrogen addition with a 95-day incubation. This suggests that nitrogen addition is required and able to sustain BWO. Besides, the cumulative oxygen consumption showed a good linear relationship with mass loss. This study provides the first indication on the effective quantify of nitrogen addition for enhancing BWO, which contributes to the selection of nutrient source for BWO in future studies.

Composting is an effective process for treating organic solid waste (OSW). There is a growing interest in recovering and reusing heat from composting, in the context of climate change and fossil fuel depletion. Several literature reviews have been conducted to address the composting process; however, several engineering aspects, including heat estimation, recovery, and utilization, are inadequately addressed in current reviews. To fill this knowledge gap, we bring together the current knowledge on the heat from composting and provide a discussion on the methods for calculating the heat potential of OSW, estimating the amount of heat production and recovering the generated heat. Moreover, we summarize the utilization of generated heat and point out the challenges and the outlook for future research. The results show that the heating value of different OSW can be calculated by ultimate analysis, proximate analysis, or composition analysis. Moreover, different methods have been used for heat production estimation: the degradation method can adequately describe the composting process, O2 method is simpler to implement, and heat balance method is only valid at large scale reactors. Different types of reactors use different techniques for heat recovery: water jacket method is suitable for small-scale reactors, while tube buried-in pile method and percolation water method are especially suitable for lignocellulosic biomass composting. Heat exchanger in the head space method and low-temperature heat recovery technologies are mainly used for commercial reactors. The heat recovered from composting is potentially suitable for building applications such as hot water service, flooring heating and wall heating.

To improve the reducing sugar production from catalpa sawdust, thermo-chemical pretreatments were examined and the chemicals used including NaOH, Ca(OH)2, H2SO4, and HCl. The hemicellulose solubilization and cellulose crystallinity index (CrI) were significantly increased after thermo-alkaline pretreatments, and the thermo-Ca(OH)2 pretreatment showed the best improvement for reducing sugar production comparing to other three pretreatments. The conditions of thermo-Ca(OH)2 pretreatment and enzymatic hydrolysis were systematically optimized. Under the optimal conditions, the reducing sugar yield increased by 1185.7% comparing to the control. This study indicates that the thermo-Ca(OH)2 pretreatment is ideal for the saccharification of catalpa sawdust and that catalpa sawdust is a promising raw material for biofuel.

High-pressure homogenization (HPH) and alkaline-heat were both used to pretreat grass clipping in order to improve the efficiency of enzymatic hydrolysis and biogas production. Results showed that both methods were very effective. HPH and alkaline-heat pretreated grass clipping yielded 230.39 and 415.93 mg g−1 reducing sugar with enzymatic hydrolysis, showing 37.82% and 148.81% increase respectively. HPH and alkaline-heat pretreated grass clipping produced 418 and 405 ml biogas in anaerobic digestion respectively, both around 2.5 times higher than that of the control. Furthermore, both pretreated samples produced biogas immediately while the control had a two-day delay. HPH could produce more biogas in a shorter time and it could be operated in room temperature and needs no chemical, implying that HPH could be an effective pretreatment of biomass for biogas production.

To improve the biogas production from corn stovers, a new bionic reactor was designed and constructed. The bionic reactor simulated the rumen digestion of ruminants. The liquid was separated from corn stovers and refluxed into corn stovers again, which simulated the undigested particles separated from completely digested materials and fed back again for further degradation in ruminant stomach. Results showed that the bionic reactor was effective for anaerobic digestion of corn stovers. The liquid amount and its reflux showed an obvious positive correlation with biogas production. The highest biogas production rate was 21.6 ml/gVS-added d, and the total cumulative biogas production was 256.5 ml/gVS-added. The methane content in biogas ranged from 52.2% to 63.3%. The degradation of corn stovers were greatly enhanced through simulating the animal digestion mechanisms in this bionic reactor.

The B Corporation movement completed a decade in 2018. Scholarly interest in B Corporations and Benefit Corporations (hereafter B Corps) has kept pace with the proliferation of certified B Corps ac...

Catalpa sawdust, a promising biofuel production biomass, was pretreated by microwave-water, -NaOH, and -Ca(OH)2 to enhance enzymatic digestibility. After 48h enzymatic hydrolysis, microwave-Ca(OH)2 pretreated sample showed the highest reducing sugar yield. The content of hemicellulose and lignin in catalpa sawdust decreased after microwave-alkali pretreatment. SEM observation showed that the catalpa sawdust surface with microwave-Ca(OH)2 pretreatment suffered the most serious erosion. Crystallinity index of catalpa sawdust increased after all three kinds of pretreatment. The optimum conditions of microwave-Ca(OH)2 pretreatment were particle size of 40mesh, Ca(OH)2 dosage of 2.25% (w/v), microwave power of 400W, pretreatment time of 6min, enzyme loading of 175FPU/g, and hydrolysis time of 96h, and the reducing sugar yield of microwave-Ca(OH)2 pretreated catalpa sawdust reached 402.73mg/g, which increased by 682.15% compared with that of raw catalpa sawdust. The catalpa sawdust with microwave-Ca(OH)2 pretreatment is promising for biofuel production with great potential.