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The Australian Red Meat Processing (RMP) industry is challenged with ever increasing environmental pressures to reduce their environmental footprint. Wastewater is high strength and requires qualit...

This article explores the potential of producing domestic, home-scale biogas using anaerobic digestion in the suburbs of the developed world – an urban context where currently biogas production is almost non-existent. The current status of food waste management across the globe shows that internationally, cities are increasingly using anaerobic digestion as a central technology at commercial scale to treat food waste and decarbonise through the recovery of energy and nutrients. However, in order to achieve this, it is preferable to separate organic waste such as food waste from other waste streams. Australia currently does not offer any schemes that support source separation of household food waste. Notwithstanding this, there are upwards of five large-scale plants currently treating commercial food waste and substantial scope exists to increase this provided appropriate waste management strategies are put in place. Nevertheless, the absence of food waste management schemes in developed countries may provide an impetus for individuals in urban landscapes to explore the potential of home-style biogas systems to produce energy and biofertiliser using food waste derived from households. This article provides a novel case study of one operator's experience using a domestic system, the ‘HomeBiogas 1.0’ unit, in the suburbs of Melbourne, Australia. A critical analysis of the system was performed, including a cost benefit analysis of the recently released ‘HomeBiogas 2.0’ unit. The cost benefit analysis indicated that the system could pay for itself in 4.45 years if simply mitigating the cost of natural gas. This payback period is likely to be reduced if the value of fertiliser were included or if use of a HomeBiogas unit allows for disconnection from the gas grid (avoiding service fees), as it did in this case study. The paper concludes by identifying barriers from a technical, regulatory and education perspective.

A key environmental sustainability requirement for the treatment of organic waste via anaerobic digestion (AD) is the prevention of unwanted methane emissions in the production chain whenever possible. Identifying and quantifying these emissions has been frequently investigated, particularly in Europe. However, the challenges of climate change are also becoming vitally important in Australia. This novel study presents the results from emission measurement campaigns carried out at two biogas plants and one landfill site in Australia. An on-site approach consisting of leakage detection and emission quantification by a static chamber method was applied. Twenty-nine leakages were detected predominantly on the digesters (gastight covered anaerobic lagoons) of the biogas plants. Ten emission hot spots were found on the surface cover of a landfill site. Methane emission rates of 9.9 ± 2.3 kg h−1 (10.5 ± 2.4% CH4) for biogas plant A, 3.0 ± 1.9 kg h−1 (8.1 ± 5.2% CH4) for biogas plant B and 41–211 g h−1 for the two largest emission hot spots from the landfill were measured. Since not every single leakage or hot spot could be quantified separately, the stated overall emission rates had to be extrapolated. Importantly, the emission rates from the landfill should be interpreted carefully due to the limited overall area which could be practicably investigated. Leakages occurred at common components of the covered anaerobic lagoons such as the membrane fixation or concrete walls. Repairing these parts would increase the plant safety and mitigate negative environmental effects.

This study presents results from lab-scale studies and highlights issues related to process monitoring equipment and analytical methods at the field scale. This includes the evaluation of data from on-site online sensors and sample analyses as well as results from discontinuous and continuous digestion tests in a biogas laboratory. The results demonstrate the influence of the organic loading and wastewater composition on process stability, sludge activity, and biogas production. Key recommendations for plant operation include the avoidance of strong fluctuations in input volume and concentration, to ensure good functioning of online sensors, and to adapt the management of the different wastewater streams according to their characteristics.

On-farm, intensive feeding and processing in Australian red meat, dairy and pork industries produce substantial quantities of organic waste (∼79 GL·annum−1 liquid waste plus ∼2 megatonnes·annum−1 solid waste) and waste management is a major cost (∼180 million Australian dollars. annum−1 for red meat plus dairy processing). Anaerobic digestion can instead extract value from organic waste as biogas energy and biofertiliser to reduce operational costs and environmental impacts, and to improve industry profitability. Understanding key information gaps is a fundamental step towards fully realizing profitable opportunities for anaerobic digestion. This is addressed here via a critical evaluation of available information on Australian agro-industries (specifically dairy, pork and red meat), their waste availability, biogas energy potential, and potential anaerobic digestion approaches. The analysis revealed varying extents of information, but good biogas energy potential (∼13.8 PJ·annum−1) to meet a significant energy demand (∼18 PJ·annum−1). Waste management within respective agro-industries influenced waste amounts and characteristics, which affected anaerobic digestion options. Anaerobic co-digestion, involving aggregated digestion of two or more waste types within or across industries, can provide further opportunities by boosting biogas production and harnessing spare digestion capacity. Overall, cross-industry collaboration, policy support and technology development could help harness the significant opportunities for aggregated biogas production in Australian agro-industries.

The livestock sector is a fundamental part of the modern global economy and provides food, clothing, furnishings, and various other products. So as to ensure its resilience to changes in consumer expectations, cost of production, and environmental sustainability, the sector must shift to a circular economy model. Current strategies to recover value from wastes and low-value co-products from livestock industries yield limited value; hence, new technologies are required to upgrade wastes and co-products, and generate high-value products that can feed into the livestock value chain. Anaerobic digestion can convert high organic-content waste to biogas for energy and a stable nutrient-rich digestate that can be used as fertiliser. Microbial technologies can transform wastes to produce nutritionally advanced feeds. New materials from waste can also be produced for livestock industry-specific applications. While aiming to add commercial value, the successful implementation of these technologies will also address the environmental and productivity issues that are increasingly valued by producers and consumers.

In this study, anaerobic digestion of slaughterhouse wastewater with the addition of trace elements was monitored for biogas quantity, quality and process stability using CSTR digesters operated at mesophilic temperature. The determination of trace element concentrations was shown to be deficient in Fe, Ni, Co, Mn and Mo compared to recommendations given in the literature. Addition of these trace elements resulted in enhanced degradation efficiency, higher biogas production and improved process stability. Higher organic loading rates and lower hydraulic retention times were achieved in comparison to the control digesters. A critical accumulation of volatile fatty acids was observed at an organic loading rate of 1.82 g L–1 d–1 in the control compared to 2.36 g L–1 d–1 in the digesters with trace element addition. The improved process stability was evident in the final weeks of experimentation, in which control reactors produced 84% less biogas per day compared to the reactors containing trace elements.

This paper explores pre-treatment options for the anaerobic digestion (AD) of high-fat cattle slaughterhouse wastewater by assessing and attempting to compare pre-treatment methods used to treat various waste streams. The central focus on cattle slaughterhouse wastewater stems from the problematic nature of high fat, oil and grease (FOG) present in Australian red meat processing (RMP) waste water. Fully integrated abattoirs such as those operating in Australia typically produce wastewaters that carry high FOG loads of 100–4000+ mg/L. While excessive levels of fat can be inhibitory to the AD process, these fats contain a very high theoretical methane potential of 1014 L CH4/kg VS when compared with carbohydrates at 370 L CH4/kg VS and proteins at 740 L CH4/kg VS. However, due to the hydrophobic and inhibitory nature of fat, oil and grease, accessing this methane potential is difficult. This article serves as a review of the literature in the field of pre-treatment of wastewaters and subsequent anaerobic digestion with the goal of increasing biogas yield, with an emphasis on digestion of wastes high in fat, oil and grease. This review covers mechanical pre-treatments including high-pressure homogenisation, ultrasonication and electrokinetic disintegration, and other forms of pre-treatment including thermal, chemical, thermochemical, and enzymatic hydrolysis, and biochemical emulsification. Biological pre-treatments, also known as pre-hydrolysis and two stage digestion are briefly reviewed. The most significant considerations for selecting a pre-treatment technology are the energy balance and costs. Therefore, this review will also provide a commentary on the advantages and disadvantages of the pre-treatment methods reviewed and conclude by evaluating their relative worth in pre-treating FOG.

Operations at meat processing plants result in the production of a range of solid and liquid wastes. Traditional solid waste management practices in Australia include rendering of offal, bones and blood into saleable products (example bone meal), composting (on-site and off-site) and off-site disposal whereas wastewater is treated on-site using anaerobic lagoons. The last decade has seen considerable interest in alternative technologies for the treatment of solid and liquid waste driven by a range of factors including rapidly increasing energy and fertilizer costs, increasing costs of disposal, odor emission and urban encroachment onto traditional rural areas and the potential for improved regulatory compliance. This work provides an overview of closed-loop opportunities for the production of bioenergy and bioproducts using solid and liquid waste at Australian red meat processing facilities. Our investigations undertaken at one of Australia’s largest processing plants have centered on developing tools and practices that better manage waste streams. This work will present results on biogas process optimization of a covered high rate anaerobic lagoon including addition of trace elements and investigation of crust management strategies. The use of solid organic waste in co-digestion and investigations into the reuse of paunch as a fertilizer are also provided. In addition, a review of value added products in the form of blood products was carried out to identify new opportunities in this area.

Low-rate anaerobic digestion technology can be influenced by environmental conditions, most notably temperature. The effect of temperature on lipid degradation and crust formation in lagoon digesters treating red meat processing (RMP) wastewater is especially pronounced, impacting on the anaerobic digestion process, resulting degradation and biogas generation. This study investigates the effect of temperature reduction from 38 °C to 25 °C to simulate the annual seasonal temperature range experienced in a covered anaerobic lagoon treating slaughterhouse wastewater located in South-East Queensland, Australia. A step-wise temperature reduction was carried out over a three-month period in continuous stirred tank reactors, and anaerobic digestion performance was compared to digesters operating at optimal mesophilic conditions. After reaching the minimum seasonal temperature, the organic loading rate was increased to identify the limits for organic loading at the different temperature levels. Lower temperatures had a negative impact on degradation efficiency, biogas production, and process stability. The translation of lab scale results to commercial scale operation indicated a 30% reduction in biogas production at a temperature of 31 °C, which corresponded to the highest annual temperatures in the covered anaerobic lagoon. A further decrease to 25.5 °C, which represents the lowest annual temperature in the lagoon, with an increase of the organic loading rate caused up to 80% difference in gas production and negatively influenced process stability. Economic assessment indicated that by operating lagoons under optimal mesophilic conditions, natural gas consumption could be offset with biogas to reduce yearly expenditure of natural gas by up to 25.4%.

Covered anaerobic ponds offer significant advantages to the red meat processing industry by capturing methane rich gas as a fuel source for bioenergy while reducing greenhouse gas emissions (GHG). This paper presents the results of a novel-designed anaerobic pond system at an Australian abattoir in relation to pond performance and potential biogas production. Key findings in assessing the effectiveness of the system revealed that the covered ponds are capable of efficient wastewater decomposition and biogas production. The primary issue with the covered ponds at the abattoir was the build-up of fat/crust that prevented the accurate measurement of biogas and effective use of the cover. In the absence of field biogas data the novel application of the computer modelling software BioWin® was carried out to simulate chemical oxygen demand(COD) removal rates and subsequent biogas yield. The unique parameter used to fit field data was the fraction of the inlet COD due to a superficial crust which did not follow anaerobic digestion. Field data effluent COD removal rates were matched to simulated rates predicted by BioWin when measured influent COD was reduced to 30%. Biogas modelling results suggest significant variation in the economic benefit of biogas energy, with the quantity of biogas potentially varying tenfold (from 328 m3/d to 3284 m3/d) depending on site factors such as pond efficiency, pond configuration and operational practices.

Due to the high strength nature of abattoir wastewater, the accumulation of crusts on anaerobic ponds is a systemic problem in the red meat processing industry in Australia and can limit the ability to accurately obtain biogas measurements. In this study, BioWin was used to simulate chemical oxygen demand (COD) removal rates and subsequent biogas production rate based on field data from two abattoirs where crust accumulation was an issue. BioWin is a Microsoft Windows-based simulator developed by EnviroSim Associates Ltd, which has seen use in the design and optimisation of wastewater treatment plants. In assessing overall anaerobic decomposition efficiency it was hypothesised that a large percentage of influent COD was present as a surface crust which remained largely unbiodegradable. Field data effluent COD removal rates were matched to simulated rates predicted by BioWin when measured influent COD was reduced to 30% (absolute relative error of 11–14%), thus supporting the notion that a significant portion of COD is not taking part in the anaerobic digestion process. The simulation provides a preliminary assessment of pond performance in terms of COD removal rates and also subsequent biogas production rates. BioWin was able to predict approximate biogas production rates ranging between 113 to 173 m3/d and 52 m3/d for the two abattoirs investigated. Further work to validate simulation using BioWin includes obtaining actual biogas measurements and performing COD measurement of crust.

Churchill Abattoir Pty Ltd (CA) is a beef abattoir and rendering facility that has operated for 43 years as a government entity, and for the past 11 years as a private enterprise. Since the changeover, there have been significant improvements in CA's environmental performance. In response to improving waste treatment and minimisation, CA has developed a novel covered anaerobic pond design for the treatment of abattoir wastewater. This design consists of five smaller ponds arranged in a cell configuration which has been driven by a number of factors including, manageability (for desludging ponds) and ease of removing and applying covers. Industry design and management standards are based on generalised metrics for anaerobic ponds rather than industry specific data. To inform pond design, an intensive study of pond behaviour was performed on the covered anaerobic ponds. This paper gives an overview of the literature reported on the use of anaerobic ponds in the treatment of high-strength wastewater and outlines the key findings in the preliminary assessment of the behaviour and performance of these novel anaerobic ponds. The use of five smaller ponds instead of one larger pond has proven successful in terms of crust and sludge removal. The primary issue with the covered ponds at Churchill, however, was the build-up of fat/ crust that prevented the capture of biogas and effective use of the cover. Despite the operational difficulties in relation to fat/crust accumulation, results indicate that satisfactory, stable operation has been achieved for the smaller five-pond system, notwithstanding the higher than desired organic loading rate of the two primary ponds.