Anaerobic Digestion Of Municipal Waste Research Articles

Fast anaerobic digestion of complex substrates via immobilized biofilms in a novel compartmentalized reactor design

Anaerobic digestion of municipal waste is a promising technology for renewable energy production, notably for methane (CH4) production. Existing reactor designs have limitations that prevent efficient conversion and high throughput, especially of substrates high in suspended solids. Here, we introduce a novel compartmentalized reactor design encompassing controlled feed flow over fixed microbial biofilms for high rate CH4 production from enzymatically pre-hydrolyzed municipal solid waste. In a 240 L working volume reactor, the biofilm generation was completed in less than 60 days and CH4 production was minimum ∼700 L day−1 in the ensuing months with a Hydraulic Retention Time (HRT) of 10 days or lower. When the organic load was gradually increased, a reactor productivity of 6 LCH4 Lreactor−1 day−1 was achieved. At this point, the reactor processed 20.8 gCOD Lreactor-1 day−1 at a HRT below 5 days, maintaining above 70% of the maximal Chemical Oxygen Demand (COD) conversion rate. Such fast conversion rates and high yields are far beyond what has been reported for other reactor designs, and are a crucial prerequisite for industrial realization of renewable biogas production from municipal solid waste and other organic waste streams.

Environmental assessment of waste feedstock mono-dimensional and bio-refinery systems: Combining manure co-digestion and municipal waste anaerobic digestion

Organic municipal solid waste (OMSW) as a feedstock for energy recovery and material recycling offers the potential to reduce environmental impacts from energy production while displacing emission-intensive waste management strategies such as landfills. This paper quantifies the environmental impact of anaerobic digestion of local, residual biomass. A life-cycle assessment was jointly performed for two scenarios for the biological treatment of local organic municipal solid waste and pig manure in the Netherlands. Scenario 1 was a separate treatment using anaerobic digestion, and Scenario 2 was a bio-refinery system that integrates anaerobic digestion of organic, municipal solid waste, and co-digestion of pig manure and other organic co-substrates∖. For both scenarios, electricity and heat are generated using a combined heat and power engine. The bio-refinery system (Scenario 2) contribution to climate change resulted in 0.16 Mt CO2 eq./yr, which is lower than the 0.17 Mt CO2 eq./yr of Scenario 1. Both scenarios are found to be beneficial with regard to resource depletion and human toxicity. The integration of organic waste and manure anaerobic digestion has no effect on acidification and terrestrial eutrophication impact categories, resulting in 43.59 AE eq. and 86.33 AE eq. for Scenario 1 and 43.58 AE eq. and 86.30 AE eq. for Scenario 2. Moreover, Scenario 2 yields 18% lower emissions than those from natural gas derived electricity in the Netherlands. The biorefinery system represents an opportunity to improve organic waste-management strategies, at the same time as reducing the environmental impact from energy production and the costs for surplus manure disposal by producing high-quality commodities that can be traded on the market.

A methodology for estimating the carbon footprint of waste collection vehicles under different scenarios: Application to Madrid

This paper proposes a methodology to calculate the impact on climate change associated with the MSW collection and transport fleet, using the Life Cycle Assessment (LCA) methodology. The proposed methodological procedure was applied to the past and present situation in Spain, taking the city of Madrid as a characteristic example. The boundaries of the system include both the fuel life cycle (FLC) and the vehicle life cycle (VLC), the emissions for which are calculated using the GlobalTRANS tool developed at the Technical University of Madrid (UPM).In the city of Madrid, MSW transport vehicles run solely on compressed natural gas (CNG). The fleet’s carbon footprint (CF) is 25.1kgCO2eq/tMSWcollected, 92% of which stems from the FLC and the remaining 8% from the VLC. In terms of the FLC, 86% of the impact comes from the Tank-to-Wheel (TtW) stage and 14% from the Well-to-Tank (WtT) stage. The raw material extraction, manufacturing and transport processes account for 67% of total VLC greenhouse gas (GHG) emissions.The situation in the city of Madrid in 2013 is compared to that in other Spanish cities and to past scenarios in Madrid, when vehicles ran on diesel. The DIESEL scenario yields emissions that are 18.5% higher than those of the CNG scenario, which means the CF would rise to 29.7kgCO2eq/tMSW. A possible future scenario where CNG is replaced by purified biogas from the anaerobic digestion of municipal waste (BIOGAS scenario) was also evaluated. In this case, CF is 92% lower.

Isolation and characterization of surface‐active fractions responsible for foam formation during anaerobic digestion of municipal wastes

A simple and rapid method to isolate surfactant‐like fractions responsible for foaming production during anaerobic digestion (AD) is proposed. Alkaline extraction of organic matter and subsequent fractionation of extracts into alkali‐soluble/acid‐insoluble (humic acid, HA) and alkali‐soluble/acid‐soluble fractions (fulvic acid, FA) were performed on samples directly taken from a full‐scale plant operating anaerobic digestion. Lab‐tests performed to measure foaming ability of the isolated organic fractions, allowed the separation of the fraction responsible for foam production, fulvic acid. Fraction isolation and subsequent chemical characterization revealed its specific chemical nature, i.e. high hydrophobicity, due to low carboxylic group content, and the presence of high N‐containing molecules. These characteristics agreed with those reported in the literature for molecules responsible for foam formation during anaerobic digestion, confirming the ability of this simple fractionation procedure to isolate the fraction responsible for foam formation.Foam formation during anaerobic digestion (AD) represents a problem for AD plants, reducing process efficiency, and increasing operational costs.The proposal of a simple and rapid procedure to isolate the fraction responsible for foam production is useful because it allows better characterizing this fraction from a chemical point of view. Knowledge of the chemical nature of the foaming agent is an important factor contributing towards developing successful antifoaming strategies. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 359–365, 2017

Modelling of a CHP SOFC system fed with biogas from anaerobic digestion of municipal waste integrated with solar collectors and storage unit

Modelling of a CHP SOFC system fed with biogas from anaerobic digestion of municipal waste integrated with solar collectors and storage unit

Modelling of a CHP SOFC System Fed with Biogas from Anaerobic Digestion of Municipal Waste Integrated with Solar Collectors and Storage Unit

The paradigm of the sustainable energy community is recognized as the future energy approach due to its economical, technical and environmental benefits. Future systems should integrate renewable energy systems applying a “community-scale” approach to maximize energy performances, while minimizing environmental impacts. Efforts have to be directed toward the promotion of integrated technical systems needed to expand the use of renewable energy resources, to build sustainable local and national energy networks, to guarantee distribution systems for urban facilities and to reduce pollution. In this framework poly-generation is a promising design perspective, for building and district scale applications, in particular where different types of energy demand are simultaneously present and when sufficient energy intensity justifies investments in smart grids and district heating networks. In situ anaerobic digestion of biomass and organic waste has the potential to provide sustainable distributed generation of electric power together with a viable solution for the disposal of municipal solid wastes. A thermal recovery system can provide the heat required for district-heating. The system analysed is a waste-to-energy combined heat and power (CHP) generation plant that perfectly fits in the sustainable energy community paradigm. The power system is divided in the following sections: a) a mesophilic - single phase anaerobic digestion of Organic Fraction of Municipal Solid Waste for biogas production; b) a fuel treatment section with desulphurizer and pre-reformer units; c) a Solid Oxide Fuel Cell (SOFC) for CHP production; d) a solar collector integrated system(integrated storage system - ISS). An integrated TRNSYS/ASPEN Plus model for simulating the power system behaviour during a typical reference period (day or year) was developed and presented. The proposed ISS consists of a solar collector integrated with storage systems system designed to continuously provide the thermal power required by the anaerobic digester.

Techno-economic evaluation of ultrasound and thermal pretreatments for enhanced anaerobic digestion of municipal waste activated sludge

To enhance the anaerobic digestion of municipal waste-activated sludge (WAS), ultrasound, thermal, and ultrasound+thermal (combined) pretreatments were conducted using three ultrasound specific energy inputs (1000, 5000, and 10,000kJ/kg TSS) and three thermal pretreatment temperatures (50, 70 and 90°C). Prior to anaerobic digestion, combined pretreatments significantly improved volatile suspended solid (VSS) reduction by 29–38%. The largest increase in methane production (30%) was observed after 30min of 90°C pretreatment followed by 10,000kJ/kg TSS ultrasound pretreatment. Combined pretreatments improved the dimethyl sulfide (DMS) removal efficiency by 42–72% but did not show any further improvement in hydrogen sulfide (H2S) removal when compared with ultrasound and thermal pretreatments alone. Economic analysis showed that combined pretreatments with 1000kJ/kg TSS specific energy and differing thermal pretreatments (50–90°C) can reduce operating costs by $44–66/ton dry solid when compared to conventional anaerobic digestion without pretreatments.

The Composting Treatment of Residue from Biological Municipal Waste Anaerobic Digestion

The high-solids anaerobic digestion of biological municipal waste (BMW) produces both a valuable fuel production (methane) and an anaerobic digestion residue. Compost technology was chosen to treat with anaerobic digestion residue and the conclusion was. 1) The anaerobic digestion of the bio-waste as a whole worked fine during the stabilization stage, the maximum daily gas production happened on the 125th day, the maximum was 91.86L/d and TS concentration in the digestive juice was14.78%, methane concentration was about 50-55%, HRT was 20 days and the biodegradation rate was 65.28%;2) The temperature of AD residue compost entered the thermophilic phase(55°C) on day 3 of composting, lasted at least 3days, the changes in pH followed the same trend with a rise from 6.18 to 7.26 on the 14th day, he final mass loss was 30.12%, which resulted in the compost quality higher than innocuity criteria.

Inhibition of mesophilic solid-substrate anaerobic digestion by ammonia nitrogen

This work focused on determining the effects of ammonia-nitrogen supplementation on the mesophilic solid-substrate anaerobic digestion of municipal wastes and waste activated sludge (biosolids). Bench-scale, semi-continuous, mesophilic reactors were operated with a 21-day mass-retention time and dosed with NH4Cl, such that the corresponding chemical O2 demand (COD)/N ratios in their feeds were 90, 80, 65 and 50 (reactors R1 or control, R2, R3 and R4 respectively). Reactor performance was evaluated in terms of the efficiency of volatile solid removal (efficiency for short), biogas productivity, methane content in the biogas, pH and volatile organic acid contents, among other monitoring and analytical parameters. The feedstock was a mixture of urban wastes with biosolids. It was found that the process performance deteriorated at increasing dosages of ammonia N, the process practically ceasing at COD/N = 50 (R4). Inhibition was characterized by efficiency and biogas productivity decreases and a more sudden drop of methane content in biogas and pH. A significant rise of propionic, butyric and valeric acid was found in reactors receiving the highest doses of ammonia N (R3 and R4). This suggested that inhibition of the syntrophic bacteria present in the anaerobic consortia also occurred. Luong and Pearson inhibition models were fitted to the data. Both models represented very well the acute effects of N supplementation on solid-substrate anaerobic digestion. However, the Luong model could also represent the process ceasing at a critical ammonia N concentration of 2800 mg/kg mixed solids.

Solid waste fermentation with particular emphasis on potentials for developing countries

Cities of Developing Countries produce around 5000 tons of municipal wastes per day. The treatments used are the dumping in the open, incineration at high costs and low caloric value, aerobic composting fairly suited to dry climates, and anaerobic digestion. In this case 1 ton of the organic fraction of the waste produces 170 m3 of biogas. The available technologies for the anaerobic digestion of municipal wastes are: (1) the conventional completely mixed digester that converts a waste problem into a water problem by using 10 tons of water for 1 ton of waste; (2) the two-step digester; (3) dry digestion, either in landfills where it is spontaneous and lasts 20 to 50 years before complete recovery or in semi-continuous digesters where biogas is recovered in three weeks. At present there exist two examples of dry digestion of municipal wastes, one in France where a 400-m3 digester works with a 35% dry matter substrate and produces 5 m3/m3 of digester per day, and the other in Gent, Belgium, where a pilot plant of 56 m3 fed with the organic fraction of municipal waste, at 35% dry matter, produces 6 m3/m3 digester per day.