Can domestic production of iLUC-free feedstock from arable land supply Sweden’s future demand for biofuels?

The increasing biofuel production from agricultural crops has been suggested to cause indirect land use change (iLUC). This increases interest in biofuel feedstocks that qualify as iLUC-free: (1) residues without a market, (2) crops from previously unused arable land, (3) additional crops and (4) biomass from intensified production. In the present study, biofuel potential from such feedstocks was quantified for Sweden and compared against the predicted biofuel demand from agricultural resources in 2030. The results indicate that straw (category 1) could cover up to 37% of future biofuel demand. Grass leys from intensified production (category 4), set-aside and abandoned land (category 2) and excess grass silage (category 1) could cover up to 79%. Intermediate and ecological focus area crops (category 3) could contribute up to 21%. To realize the biofuel targets, a high implementation rate of additional iLUC-free feedstock is needed. Future studies need to investigate impacts of low-iLUC policies.     

Barriers to the diffusion of renewable energy: studies of biogas for transport in two European cities

The diffusion of renewable energy – particularly in transport – in cities may facilitate the transition away from fossil fuels, improve air quality and reduce greenhouse gas emissions. Past studies on this topic have focused on system modelling of diffusion pathways, technology characteristics and also estimations of future availability of renewable energy, whilst neglecting the agency of producers and users. This article assesses barriers to the diffusion of biogas for transportation in cities from a system and actor perspective. Using document studies and interviews in the cities of Basel, Switzerland, and Odense, Denmark, we identify the presence of conflicting political priorities and shifting strategic objectives, resulting in mixed signals concerning the role and viability of biogas for transportation. This underlines the importance of public sector support and coherent design and implementation of strategy and policy enabling the diffusion of renewable energy.     

Comparison effect of feedstock to inoculum ratios on biogas yields of cafeteria,vegetable, fruit wastes with cattle manure using co-digestion process

Cafeteria, vegetable, fruit, and cattle manure are available year around at low cost and have the potential to complement each other for anaerobic digestion (AD). The objectives of this study were to determine the preferred mixing ratios and effects of feedstock to inoculum ratios for the optimal biogas production. The mesophilic digestion tests were performed with five mixing ratios of CW, VW, FW with CM and five feedstock to inoculum (F/I) ratios using batch anaerobic digesters. Co-digestion of CW, VW, FW with CM was carried out at F/I ratios of 1.0, 2.0, 3.0, 4.0, and 5.0. The results showed that the F/I ratio significantly affected the biogas production rate. Increasing the CW, VW, FW in the CM resulted in an increased methane yield by decreasing the F/I ratios in the reactors from 5.0 to 1.0. The highest biogas yields of 591.3, 432.9, and 450.6 L/kg VS_feed were obtained with CW/CM (50:50), VW/CM (25:75), and FW/CM (25:75) ratios, respectively. At five F/Is tested, after 45 days of AD, the total biogas yields were determined to be 629.74, 552.64, 501.87, 464.66, and 396.04 L and 496.93, 460.02, 420.5, 398.14, and 336.20 L, and 455.03, 382.81, 349.78, 340.95, and 298.53 L, respectively. However, the highest average CH₄ contents obtained at an F/I of 1.0 were 62.14%, 60.72%, and 61.08% that are 5.87%, 9.47%, and 10.17% higher than those obtained at F/I ratio of 5.0 for CW/CM (50:50), VW/CM (25:75), and FW/CM (25:75), respectively.     

The influence of dilute sulfuric acid pretreatment on biogas production from wheat plant

Dilute sulfuric acid pretreatment was used to improve the biomethane production from wheat plant (WP) via mesophilic anaerobic digestion. The pretreatments were performed at 121°C for different time durations of 10, 30, 60, and 120 min. The maximum methane yield of 302.4 mL/g volatile solids (VS) was obtained after the pretreatment for 120 min, which was 15.5% higher than that of the untreated WP. The highest amounts of lignin removal (15.2%) and xylan degradation (91.5%) were also achieved after this pretreatment. The pretreatment for 60 min enhanced the methane yield by 8.9%, while the pretreatments for 10 and 30 min had no positive effects on the methane yield. All of the pretreatments significantly removed the hemicelluloses. Moreover, the qualitative analysis of the untreated and pretreated WP structure showed significant reduction in the crystallinity index accompanied by the destruction of surface layers of WP structure after pretreatment.     

Biogas upgrading and utilization from ICEs towards stationary molten carbonate fuel cell systems

Biogas production from anaerobic digestion has increased rapidly in the last years, in many parts of the world, mainly due to its local scale disposition and to its potential on greenhouse gases (GHG) emissions mitigation. Biogas can be used as fuel for combined heat and power systems (CHP), in particular for internal combustion engines (ICEs). In recent investigations, fuel cells have been considered as alternative CHP systems. In the present article, two different energy conversion systems are compared: a 1.4 MW class MCFC system, running on pipeline natural gas, and an in situ ICE, running on biogas. In the first case, biogas is considered as a source fuel to obtain upgraded gas to be injected in the natural gas grid. In such scenario, the location of the fuel cell power plant is no longer strictly connected to the anaerobic digester site. Several energy balances are evaluated, considering different upgrading techniques and different biogas methane/carbon dioxide ratios.     

Kinetics of the biodegradation pathway of endosulfan in the aerobic and anaerobic environments

The enriched mixed culture aerobic and anaerobic bacteria from agricultural soils were used to study the degradation of endosulfan (ES) in aqueous and soil slurry environments. The extent of biodegradation was ∼95% in aqueous and ∼65% in soil slurry during 15 d in aerobic studies and, ∼80% in aqueous and ∼60% in soil slurry during 60 d in anaerobic studies. The pathways of aerobic and anaerobic degradation of ES were modeled using combination of Monod no growth model and first order kinetics. The rate of biodegradation of β-isomer was faster compared to α-isomer. Conversion of ES to endosulfan sulfate (ESS) and endosulfan diol (ESD) were the rate limiting steps in aerobic medium and, the hydrolysis of ES to ESD was the rate limiting step in anaerobic medium. The mass balance indicated further degradation of endosulfan ether (ESE) and endosulfan lactone (ESL), but no end-products were identified. In the soil slurries, the rates of degradation of sorbed contaminants were slower. As a result, net rate of degradation reduced, increasing the persistence of the compounds. The soil phase degradation rate of β-isomer was slowed down more compared with α-isomer, which was attributed to its higher partition coefficient on the soil.     

固体废弃物对新拌水泥浆体密实度与强度的影响

研究固体废弃物(石灰石粉、粉煤灰、赤泥和矿渣)作掺合料颗粒体系与新拌浆体填充密实性能的关系;分析了在水胶比为0.3时,以上4种固体废弃物以不同比例等质量取代水泥的净浆强度。实验结果表明,石灰石粉、粉煤灰、赤泥作为掺合料,能够改善胶凝材料的颗粒级配,填充新拌水泥浆体中的孔隙,使浆体更为密实,并且对其净浆的强度有利。     

户用沼气模式生命周期减排清单与环境效益分析

相对于传统农业活动,以沼气为纽带的生态农业生产具有清洁的能源生产和高度闭环的废物回收处置等明显优势,在全国范围内得到入户推广。本文综合考虑沼气工程建造、使用和综合利用等生命周期过程,分析了典型户用沼气池综合利用各阶段环境节能减排清单,并在此基础上评价其环境效益。结果表明,"猪-沼-稻-果"综合农业利用模式下单位沼气池节能减排效果明显,其中CO2、PM10、CH4和CO净减排量分别达3 060.700kg、19.820kg、12.960kg和75.590kg,总净节能达9 068.4MJ。其中,玉米秸秆、沼液沼渣的利用和燃煤替代对温室效应的减缓明显,畜禽粪便的利用和燃煤的替代减缓了环境酸化以及富营养化过程,而光化学氧化的减缓主要来自玉米秸秆的利用而减少的CO、VOC的排放,沼气工程对人体毒害的减缓主要是来自燃煤替代而减少的SO2和PM10排放。户用沼气利用对各种环境影响均有减缓作用,其中对光化学氧化、富营养化、环境酸化和温室效应的改善最为显著,对于降低能源耗竭、减缓对人体的毒性也起到了较好的作用。     

不同存放时间太湖蓝藻产沼气潜力

对不同存放时间蓝藻(新鲜蓝藻、存放3个月、6个月和9个月)进行厌氧消化处置,分析反应过程中沼气量、代谢产物和酶活等变化,获得各自的产沼气潜力。研究结果表明,存放6个月蓝藻组的产沼气率最大,为120.5 mL/g TS,是新鲜蓝藻组的1.29倍。Gompertz模型拟合表明,随着存放时间的延长,最大产沼气量(Pmax)先增大后减小,最大比产气率一直增加。存放3个月蓝藻组的VFA在第6天达到最大,为1 575.4 mg/L,而存放9个月蓝藻组的VFA在第2天达到最大,为1 116.5 mg/L。存放3个月蓝藻组的最大中性蛋白酶酶活为1 203.4μg/(g TS.h),比新鲜蓝藻组提高212.8μg/(gTS.h)。脱氢酶酶活随着蓝藻存放时间的增加呈现先增加后减小的趋势。     

生物氧化磁黄铁矿产生铁离子

从广东云浮矿山酸性废水中富集获得氧化亚铁硫杆菌(Thiobacillus ferrooxidans),利用该氧化亚铁硫杆菌研究了反应时间、pH、温度、矿浆浓度和矿物粒度对磁黄铁矿生物氧化获得铁离子的影响。结果表明,在29℃,摇床转速200 r/min,10%接种量条件下,氧化亚铁硫杆菌可以明显促进磁黄铁矿的氧化,但反应后期有黄钾铁矾沉淀生成,不利于获得铁离子;控制溶液pH值为2.00,温度在29～36℃范围,可促进生物氧化磁黄铁矿获得铁离子;铁离子量随着矿浆浓度的增大和矿物粒度的减小而增加,优化的矿浆浓度和矿物粒径分别为6%和58μm左右。