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Organic waste mostly comes from food waste, which has characteristics of high concentrations of nitrogen and fat, and high humidity. Domestic waste in Indonesia has a high organic content, which is suitable for anaerobic conditions. Waste oil and fat can be used as co-substrates and are helpful in yielding biogas in an anaerobic digestion (AD) process. The aim of this research is to analyze the performance of a food waste dry anaerobic digestion reactor after the addition of fat oil and grease (FOG) waste. The research was conducted using a semi-continuous stirred tank reactor (SCSTR) with an active volume of 400 L, operated at an average temperature of 27.8±1.07oC. Two experimental scenarios were performed, using varying types of food waste, food waste with cow dung as substrate, and FOG waste as co-substrate. The experiment was conducted using an Organic Loading Rate (OLR) of approximately 10 kg VS/m3, with a constant mixing intensity of 30 rpm. The results show that there was a significant difference between the input of food waste substrate with and without the addition of FOG (p

Abstract Informed by the European Union's waste hierarchy, UK policy has normatively shifted the ontological status of waste from matter out of place to a resource for which uses must be found in order to achieve environmental goals of decarbonisation and waste reduction. Technologies linking waste-management with renewable energy have been supported within an ecomodernist framework of market incentives for stimulating private-sector investment in new waste treatment technologies. Under pressure of EU targets, the UK's policy measures have had several aims: to reduce landfill disposal, increase resource recycling or reuse, expand waste-based renewable energy and thus reduce GHG emissions. As techno-market-fixes, new facilities were meant to convert waste for more beneficial uses, bring it up the hierarchy and localise its management. Consequent tensions can be illuminated by linking concepts of technology scaling and socio-material metamorphosis with critical perspectives on ecomodernism. Although the ecomodernist framework stimulated some waste-management improvements, other outcomes contradict the policy objectives of localising and converting waste for more beneficial uses. These contrary outcomes are illustrated by two technologies, anaerobic digestion (AD) and mechanical and biological treatment (MBT), each with multiple possible spatial scalings and techno-configurations. Financial instruments have most incentivised the easiest socio-material metamorphosis for lucrative returns, especially to produce energy (electricity or gas) for grid systems, suiting large operators. For more environmentally beneficial uses of waste, there have been difficulties in overcoming its recalcitrance for producing commercially viable outputs, e.g. digestate replacing chemical fertilisers, compost improving soil and 'dirty' plastics replacing virgin plastics. Techno-configurations and material flows have been scaled towards global goods, distant from the feedstock source. Through the ecomodernist framework, the state's responsibility for such outcomes has been blurred with the private sector and shifted to anonymous markets. [ABSTRACT FROM AUTHOR]

The effect of calcium peroxide (CaO 2 ) addition on anaerobic digestion (AD) of waste activated sludge (WAS) at different temperatures (20 °C, 35 °C, and 55 °C) were investigated. The results show that CaO 2 addition had significant positive effect on short-chain fatty acids (SCFAs) production under ambient and mesophilic conditions. Polysaccharides and proteins embedded in extracellular polymeric substances (EPS) were effectively released from inner fraction to outer fraction, and non-biodegradable humic-like substances were decreased while easily biodegradable tryptophan-like proteins increased. These effects were most remarkable under ambient conditions. However, CaO 2 addition was unfavorable to thermophilic AD because of high free ammonia concentrations and the accumulation of humic-like substances. Temperature showed a stronger effect than CaO 2 on microbial community structure, but CaO 2 addition was more effective than temperature in enhancing hydrolytic and acidifying microorganisms. Predictive functional profiling indicated that microbial hydrolysis, metabolism and acidification were promoted by CaO 2 under ambient conditions. [ABSTRACT FROM AUTHOR]

Organic waste mostly comes from food waste, which has characteristics of high concentrations of nitrogen and fat, and high humidity. Domestic waste in Indonesia has a high organic content, which is suitable for anaerobic conditions. Waste oil and fat can be used as co-substrates and are helpful in yielding biogas in an anaerobic digestion (AD) process. The aim of this research is to analyze the performance of a food waste dry anaerobic digestion reactor after the addition of fat oil and grease (FOG) waste. The research was conducted using a semi-continuous stirred tank reactor (SCSTR) with an active volume of 400 L, operated at an average temperature of 27.8±1.07°C. Two experimental scenarios were performed, using varying types of food waste, food waste with cow dung as substrate, and FOG waste as co-substrate. The experiment was conducted using an Organic Loading Rate (OLR) of approximately 10 kg VS/m3, with a constant mixing intensity of 30 rpm. The results show that there was a significant difference between the input of food waste substrate with and without the addition of FOG (p<0.05). The average reduction of volatile solids (VS) and chemical oxygen demand (COD) removal in the substrate input with FOG addition was higher than without the addition. The mean percentages of COD removal and VS reduction in the substrate input with FOG addition were 63.3±2.71% and 89.30±1.55%, whereas those for substrate input without FOG addition were 59.45±4% and 77.65±1.46%, respectively. The study concludes that the use of FOG as a co-substrate in a dry AD food waste reactor is not only beneficial in reducing FOG waste generation, but also has a significant impact on reducing COD and VS, which can enhance potential biogas yield. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonisation (HTC) has been identified as a potential route for digestate enhancement producing a solid hydrochar and a process water rich in organic carbon. This study compares the treatment of four dissimilar digestates from anaerobic digestion (AD) of agricultural residue (AGR); sewage sludge (SS); residual municipal solid waste (MSW), and vegetable, garden, and fruit waste (VGF). HTC experiments were performed at 150, 200 and 250 °C for 1 h using 10%, 20%, and 30% solid loadings of a fixed water mass. The effect of temperature and solid loading to the properties of biocoal and biochemical methane potential (BMP) of process waters are investigated. Results show that the behaviour of digestate during HTC is feedstock dependent and the hydrochar produced is a poor-quality solid fuel. The AGR digestate produced the greatest higher heating value (HHV) of 24 MJ/kg, however its biocoal properties are poor due to slagging and fouling propensities. The SS digestate process water produced the highest amount of biogas at 200 °C and 30% solid loading. This study concludes that solely treating digestate via HTC enhances biogas production and that hydrochar be investigated for its use as a soil amender.

The current concerns on global energy security, climate change, and environmental pollution represent some of the major elements of the growing interest on renewable energy. In this framework agro-food energy systems are at the center of a twofold debate: on the one hand they represent a key option for energy production while on the other their sustainability is threatened by the expansion of the bioenergy market that could lead to negative social and environmental consequences. The aim of this work is to evaluate—through a case study—the technical and economic feasibility of the replacement of energy crops (ECs) with used cooking oil (UCO) in an anaerobic digestion (AD) full-scale plant. At this purpose, a full-scale plant performing AD was monitored for two years. Three scenarios were developed and compared to evaluate the impacts and the potential benefits in terms of land saving in case of a substitution of ECs with UCO. Results highlighted a reduction of land use of over 50% if UCO is introduced in co-digestion with ECs. The lack of an appropriate legislative framework limits the utilization of used cooking oils (UCOs) in AD with a consequently missed opportunity for biogas owners that could find an important alternative in UCO. [ABSTRACT FROM AUTHOR]

The current concerns on global energy security, climate change, and environmental pollution represent some of the major elements of the growing interest on renewable energy. In this framework agro-food energy systems are at the center of a twofold debate: on the one hand they represent a key option for energy production while on the other their sustainability is threatened by the expansion of the bioenergy market that could lead to negative social and environmental consequences. The aim of this work is to evaluate—through a case study—the technical and economic feasibility of the replacement of energy crops (ECs) with used cooking oil (UCO) in an anaerobic digestion (AD) full-scale plant. At this purpose, a full-scale plant performing AD was monitored for two years. Three scenarios were developed and compared to evaluate the impacts and the potential benefits in terms of land saving in case of a substitution of ECs with UCO. Results highlighted a reduction of land use of over 50% if UCO is introduced in co-digestion with ECs. The lack of an appropriate legislative framework limits the utilization of used cooking oils (UCOs) in AD with a consequently missed opportunity for biogas owners that could find an important alternative in UCO.

The utilisation of municipal solid waste (MSW) for energy production has been implemented globally for many decades. Malaysia, however, is still highly dependent on landfills for MSW management. Because of the concern for greenhouse gases (GHG) emission and the scarcity of land, Malaysia has an urgent need for a better waste management strategy. This study aims to evaluate the energy, economic and environmental (3E) impact of waste-to-energy (WTE) for municipal solid waste management. An existing landfill in Malaysia is selected as the case study for consideration to adopt the advanced WTE technologies including the landfill gas recovery system (LFGRS), incineration, anaerobic digestion (AD), and gasification. The study presented an interactive comparison of different WTE scenarios and followed by further discussion on waste incineration and AD as the two potential WTE options in Malaysia. The 3E assessment reveals incineration as the superior technology choice when the production of electricity and heat were considered; however, AD is found to be more favourable under the consideration of electricity production only. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) can bring benefits in terms of effective management of organic waste, recovery of nutrients and energy recovery, and is consistent with circular economy principles. AD has been promoted and implemented worldwide, but at widely differing scales, influenced by the availability and location of feedstocks. In developing countries, feedstock arises from small- to medium-scale agriculture and agro-processing operations, as well as from household and municipal waste. Biogas produced from residues from agro-processing facilities may be used for on-site heat and power, but the lack of a gas and electricity grid infrastructure can limit opportunities to distribute gas or generated electricity to wider users. This paper presents the findings of the first study to consider novel technologies for small-scale and low-cost biogas clean-up into biomethane, and compression into small bottles, suitable as a clean cooking fuel. The paper reports on the initial evaluation of biomethane for cooking in Ghana and Uganda. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonisation (HTC) has been identified as a potential route for digestate enhancement producing a solid hydrochar and a process water rich in organic carbon. This study compares the treatment of four dissimilar digestates from anaerobic digestion (AD) of agricultural residue (AGR); sewage sludge (SS); residual municipal solid waste (MSW), and vegetable, garden, and fruit waste (VGF). HTC experiments were performed at 150, 200 and 250 °C for 1 h using 10%, 20%, and 30% solid loadings of a fixed water mass. The effect of temperature and solid loading to the properties of biocoal and biochemical methane potential (BMP) of process waters are investigated. Results show that the behaviour of digestate during HTC is feedstock dependent and the hydrochar produced is a poor-quality solid fuel. The AGR digestate produced the greatest higher heating value (HHV) of 24 MJ/kg, however its biocoal properties are poor due to slagging and fouling propensities. The SS digestate process water produced the highest amount of biogas at 200 °C and 30% solid loading. This study concludes that solely treating digestate via HTC enhances biogas production and that hydrochar be investigated for its use as a soil amender. [ABSTRACT FROM AUTHOR]