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.     

Gifting,ridding and the “everyday mundane”: the role of class and privilege in food waste generation in Indonesia

Current research on household food waste has not considered the impact of the inter-class power dynamics between employers and domestic helpers on food waste management and generation in the Global South. This article focuses on the issue of food justice and will demonstrate that it is important to reconsider household food practices within the framework of unequal power dynamics in household units – especially between employers and their domestic helpers. Informed by food waste regime conceptual framework, this paper will examine the complex food provisioning practices of Indonesian households. The research draws on 21 in-depth interviews with households of varying incomes, multiple site visits, participant observation and going along on grocery trips to better understand the power dynamics and practices that result in, or prevent the generation of household food waste. In addition, 12 key informant interviews with government officials, traditional food vendors, supermarket managers, and a waste collector was also conducted. In an Indonesian context, understanding the interclass dynamics of the household, namely, who gets to define what is “food” and what is “waste” is key to understanding the broader phenomenon of food waste in order to promote solutions to food waste prevention and food insecurity that is socially and environmentally just.     

Household adjustment to flood risk: a survey of coastal residents in Texas and Florida,United States

Individual households have increasingly borne responsibility for reducing the adverse impacts of flooding on their property. Little observational research has been conducted, however, at the household level to examine the major factors contributing to the selection of a particular household adjustment. This study addresses the issue by evaluating statistically the factors influencing the adoption of various household flood hazard adjustments. The results indicate that respondents with higher‐value homes or longer housing tenure are more likely to adopt structural and expensive techniques. In addition, the information source and the Community Rating System (CRS) score for the jurisdiction where the household is located have a significant bearing on household adjustment. In contrast, proximity to risk zones and risk perception yield somewhat mixed results or behave counter to assumptions in the literature. The study findings provide insights that will be of value to governments and decision‐makers interested in encouraging homeowners to take protective action given increasing flood risk.     

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.     

三峡库区农村生活垃圾处理支付意愿及影响因素分析

农村生活垃圾的集中化、科学化处理对改善农村居民生活环境和农业生产环境具有重要意义。而农户对农村生活垃圾处理的支付意愿对农村生活环境的改善具有关键性作用。采用条件价值评估法(CVM)分析了三峡库区农户对处理生活垃圾的支付意愿及其影响因素。结果表明:(1)农户对农村生活垃圾处理的平均支付意愿为48元/a;(2)户主年龄、文化程度以及对环境是否关心对当地农户处理生活垃圾的支付意愿有极显著影响。户主年龄和文化程度对生活垃圾处理的支付意愿的影响为正,说明农户年龄越大、文化程度越高,对生活垃圾处理的支付意愿就越强烈。农户对环境的关心程度为正,表示农户越关心环境,对生活垃圾处理的支付意愿就越强烈。最后,提出相关建议:制定政策时要充分考虑农户的个体特征和自身利益;加强教育,提高农户的文化水平;加强环境保护宣传,提高农户的环境认知和环保意识。     

天津市文明生态村生活垃圾处理方案优选

根据天津市文明生态村生活垃圾的特点和组成成分,以垃圾的分类收集和分类处理为前提,采用费用-效益分析法和层次分析法,对填埋、堆肥和焚烧处理方案分别进行费用-效益分析和经济、技术、环境、政策综合分析。结果表明,堆肥和焚烧的费用-效益分析得分为0.96和0.786,填埋不产生效益;堆肥、焚烧和填埋的层次分析法得分为7.74、4.28和5.45,堆肥方案的得分最高,其次为填埋,天津市文明生态村生活垃圾宜采用堆肥+填埋处理方案。     

甘南黄河水源补给区生态补偿农户参与意愿分析

生态补偿是非常有效的解决世界生态问题的政策工具集,农户作为生态补偿项目的实施主体,其参与意愿直接影响生态补偿项目的实施绩效和可持续性。甘南黄河水源补给区承担重要的生态服务功能,属国家级限制开发区,自2003年开始,实施退牧还草等生态工程。在此背景下,通过实地调研,运用二项Logistic模型进行分析,得出以下结论:①甘南黄河水源补给区农牧民对生态补偿项目的认知水平很低,主要是客观条件限制和政府宣传力度不足所致;②受生产方式的影响,甘南黄河水源补给区内,农区农户的生态补偿参与意愿强于半农半牧区、纯牧区;③对甘南黄河水源补给区农户生态补偿参与意愿影响最显著因素是农户对现行退牧还草政策的满意度,其次为农户家庭年收入、牲畜存栏数、退牧还草政策实施后的收入变化及其对生态补偿项目的支持度,再次为农牧民对生态补偿的了解度及其环境意识。基于此,提出了进一步完善生态补偿政策、提高农户参与意愿的措施,为进一步完善生态补偿机制提供借鉴。     

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。