Landfilling organic waste generates greenhouse gases and contributes to climate change. While the management of organic waste has been identified by all tiers of Australian government as paramount to meeting net zero emissions targets, diversion of domestic organic waste from landfill is primarily the responsibility of local government. This review of academic and grey literature considers developments in food organics and garden organics collections in Australia and the implications for regional communities. It reviews source-separated collections and the treatment of organic waste administered by regional local governments and identifies there is a dearth of information in this area. Key knowledge gaps emerging from the study include: (1) There is a disconnect between the various state governments’ policies, strategies, and regulation of organics diversion and action on mandating or supporting kerbside collections; (2) there is insufficient funding and subsidy to encourage councils to implement collection systems, and (3) the community has limited understanding of the cost and environmental burden of waste, and subsequently there is no willingness to pay for collection systems. This paper outlines how these issues contribute to individual regional councils deferring kerbside organic waste collection systems and offers recommendations that could enable the achievement of more ideal diversion targets that are relevant to, and affordable for, their local communities.

This work aimed to enhance the anaerobic digestion of fat-rich dissolved air flotation (DAF) sludge through chemical, thermobaric, and thermochemical pre-treatment methods. Soluble chemical oxygen demand was enhanced from 16.3% in the control to 20.84% (thermobaric), 40.82% (chemical), and 50.7% (thermochemical). Pre-treatment altered volatile fatty acid concentration by -64% (thermobaric), 127% (chemical) and 228% (thermochemical). Early inhibition was reduced by 20% in the thermochemical group, and 100% in the thermobaric group. Specific methane production was enhanced by 3.28% (chemical), 8.32% (thermobaric), and 8.49% (thermochemical) as a result of pre-treatment. Under batch digestion, thermobaric pre-treatment demonstrated the greatest improvement in methane yield with respect to degree of pre-treatment applied. Thermobaric pre-treatment was also the most viable for implementation at slaughterhouses, with potential for heat-exchange to reduce pre-treatment cost. Further investigation into long-term impact of pre-treatments in semi-continuous digestion experiments will provide additional evaluation of appropriate pre-treatment options for high-fat slaughterhouse wastewater.

Thermal treatment in Australia is gaining interest due to legislative changes, waste reduction goals, and the need to address contaminants’ risks in biosolids used for agriculture. The resulting biochar product has the potential to be beneficially recycled as a soil amendment. On-farm management practices were reviewed to identify barriers that need to be overcome to increase recycling and examine the role of pyrolysis and gasification in effectively improving the quality and safety of biochar intended for land application. Key findings revealed the following: (1) thermal treatment can effectively eliminate persistent organic pollutants, microplastics, and pathogens, and (2) more than 90% of the total heavy metals content in biosolids may become immobilized when these are converted to biochar, thus reducing their bioavailability following land application. While the reported research on the short-term effects of biosolids-derived biochar suggests promising agronomic results, there is a dearth of information on long-term effects. Other knowledge gaps include the optimization of land application rates, understanding of the rate of breakdown, and the fate of contaminants in soil and water, including heavy metal mobility and redistribution in the environment by processes such as erosion and runoff following land application. An improved understanding of nutrients and contaminants dynamics in soils receiving biosolids-derived biochar is a pre-requisite for their safe use in Australian agriculture, and therefore, it is highlighted as a priority area for future research.

This study investigated biochemical methane potential (B₀) of manure residues and solid-liquid separation fractions from Australian dairies. This is important for country-specific sector emissions and biogas potential estimates. A range of samples were collected from 12 farms across 4 Australian states, and B₀ was measured. A first B₀ value for grazing dairy effluent is reported, at 161 L_CH4·kg_VS^-1. The B₀ of manure residues from intensive dairies with total mixed ration feeding was not significantly different, at 202 L_CH4·kg_VS^-1. Passive solid-liquid separation decreased B₀ with potential fugitive methane losses. Mechanical separation preserved B₀, allowing organic matter diversion to reduce fugitive methane emissions. Cleaning method at a dairy significantly influenced residue total solids content, important for solid-liquid separation and selection of anaerobic digestion technology. Overall, B₀ for Australian dairy residues was estimated at 76.2 million m³_N methane per annum, with a total energy content of 2.8 petajoules·annum^-1.

This work represents and reviews a compilation of investigations into improving anaerobic digestion performance of high-strength wastewater in the Australian Red Meat Processing industry. The industry produces significant quantities of organic-rich wastewater which requires treatment prior to release to the environment. Anaerobic lagoons are a cost-effective method of waste treatment where land availability is not an issue; however, the high fat load in the wastewater can negatively impact the anaerobic lagoon system and result in compromised anaerobic digestion performance. This paper will discuss the importance of upstream primary pre-treatment and review a series of investigations focused on optimising digester performance and improving fat biodegradability. These studies include: 1. the effect of temperature and mixing; 2. the influence of feedstock trace element composition and supplementation, and; 3. the potential benefit from pre-treatments such as chemical, thermobaric, thermochemical and bio-surfactant. This paper discusses the implications of these findings for covered anaerobic lagoon operation and provides recommendations to promote optimum digester performance and future opportunities in adopting alternate anaerobic digestion technology options. Finally, the paper provides recent trends toward the use of other waste streams for co-digestion and discusses this in terms of digester optimization and technology options.