Agricultural applications: energy uses and audits

On-farm energy efficiency is becoming increasingly important in the context of rising energy costs and concerns over greenhouse gas (GHG) emissions. Energy inputs represent a major and rapidly increasing cost to the growers around the world. This entry reviews the currently available tools and technologies for conducting on-farm energy audits/assessments. Opportunities to reduce operational energy inputs and impacts on GHG emissions are also discussed

Managing direct energy use now and in the future

[Background and Introduction]: Agricultural producers are currently aware of increasing energy costs. This has occurred before the scientific and political debate on climate change has been resolved and a decision made on the best policy instruments to be used to respond. In parallel to this discussion, the on farm assessment of direct energy inputs (i.e. diesel and electricity) enables farmers to react positively to the potential of rising energy costs while contributing to a reduction in greenhouse gasses (GHGs) regardless of the scientific and policy debate surrounding climate change and emissions reduction. Previous work undertaken by the National Centre for Engineering in Agriculture (NCEA) has studied direct on farm energy use involving a number of case study cotton farms to understand the range, costs and contributions of energy use to cotton production and greenhouse gas emissions. The results from this work showed that energy use varies depending on the cropping enterprise and the farming system and that there are significant opportunities to reduce energy and costs. In comparison the greenhouse gas emissions (GHGs) from direct energy use can be similar and in fact greater than the GHGs generated by soil / fertiliser / water interactions. Improving on farm energy use would appear to be as important as improving nitrogen efficiency. A more detailed study undertaken by the NCEA on a large cotton farm in the Gwydir Valley (reference) identified significant reductions in energy resulting from the adoption of reduced tillage systems. The study showed that the adoption of a minimum tillage system had reduced energy costs (and greenhouse emissions) by 12% since 2000 and developing a 'near zero till' system had the potential to reduce this to 24% less than 2000 energy costs. It is evident from this work that there is substantial scope to improve energy use efficiency in cotton production systems, but to enable more growers to identify where they can improve, further development of tools, processes and human capacity is required. In the cropping sector a number of practice changes and technology developments have been, or are being, adopted which can be expected to reduce fuel / energy use or energy use intensity. Examples include minimum / zero tillage, controlled traffic, a range of precision ag technologies, planting of GM crops, some water use efficiency measures and use of legumes in crop rotations. Unfortunately, because the primary driver for the adoption of these practices and technologies has not been energy costs or efficiency, relatively few studies have considered the energy savings or efficiencies associated with them. Within highly mechanised agricultural productions systems such as the Australian Cotton Industry direct energy inputs (i.e. diesel and electricity) represent a major cost to the grower and potentially a significant proportion of the total green house gas (GHG) emissions. Previous studies by Baillie and Chen (2008) have reported significant savings in energy for both a refinement in current practices (i.e. up to 30 % for individual operations) and a change in practice (10 – 20% across the farming system) through energy assessment

Strategies for maximizing sugarcane yield with limited water in the Bundaberg district

Between 1995 and 2003 sugarcane farmers in Bundaberg had access to limited irrigation water. Over this time water allocations were effectively a quarter of the requirements for a fully irrigated crop. In response to this problem irrigation strategies were developed to assist farmers. Field investigations focused on the performance of water winch and furrow irrigation systems, which make up 91 percent of the irrigated area in the district. As most of these application systems have insufficient capacity to meet crop demands, opportunities to schedule irrigations were limited to start up after rain. Improvements in irrigation system performance were found to provide the greatest potential to increase sugarcane yield under conditions of limited water. Investigations identified that irrigation performance could be significantly improved through relatively minor adjustment. Timing of irrigation start up after rain influenced how much water could be applied to the field. Even with relatively low allocations delayed start up strategies could lead to a situation where water was left over at the end of the season

Anaerobic digestion and biogas potential: simulation of lab and industrial-scale processes

In this study, simulation was carried out using BioWin to test the capability of the software in predicting biogas potential for two different anaerobic systems. The two scenarios included; 1) a laboratory scale batch reactor and 2) an industrial scale anaerobic continuous lagoon digester. Measured data relating to operating conditions, reactor design parameters, and chemical properties of influent wastewater were entered into BioWin. A sensitivity analysis was carried out to identify the sensitivity of the most important default parameters in the software's models. BioWin was then calibrated by matching the predicted data with measured data and used to simulate other parameters which were unmeasured or deemed uncertain. In addition, statistical analyses were carried out using evaluation indices such as coefficient of determination (R-squared), correlation coefficient (r) and its significance (P value), general standard deviation (SD) and Willmott index of agreement to evaluate the agreement between the software prediction and the measured data. The results have shown that after calibration, BioWin can be used reliably to simulating both small scale batch reactors and industrial scale digesters with an absolute relative error less than 10% and very good indexes' values. Also, by changing the default parameters in BioWin, which is a way of calibrating the models in the software as well, it may provide information about the performance of the digester. Furthermore, the results of this study showed there may be an over estimation for biogas generated from industrial scale digesters. More sophisticated analytical devices may be required for reliable measurements of biogas quality and quantity

Developing life cycle inventory for life cycle assessment of Australian cotton

Life Cycle Assessment (LCA) is an internationally recognised approach for evaluating the environmental impacts of products and services. In this paper, the potential issues in the development of a consistent and comprehensive life cycle inventory (LCI) data are illustrated in the context of Australian cotton industry. These include diversity and variable nature of farming practices, and the inherent complexities such as the inter-linkages between co-products. For the implementation of LCI, the choices of functional unit and system boundary, definition of regional sub-sectors, methods of energy assessments, and rules of allocations of inputs and emissions are discussed. It is shown that for cotton production, the contribution of on-farm indirect 'chemical' inputs is particularly important, accounting for up to 50–80% of the total energy input in the life cycle. The need for quantified trade off analysis between alternative systems in the LCA context is also emphasized

Future farming: Machine vision for nitrogen assessment in grain crops

- A pilot simulation and field study demonstrated potential for machine vision to estimate in-season soil and leaf nitrogen status using cameras and image analysis for real-time sensing and control - The modelled soil and leaf nitrogen were estimated with >80% accuracy using machine vision-detectable crop features estimated in combination with known underlying soil variability - Further trials will evaluate and refine the machine vision system at the Future Farm core site

An investigation into the fertilizer potential of slaughterhouse cattle paunch

In Australia, the red meat processing industry actively seeks approaches to improve the management of solid waste from processing operations and enhance the environmental performance. Recycling of paunch waste to farmland could be a cost-effective and practicable environmental option. However, little is known about the agronomic value of fresh and composted paunch, and the associated requirements for land application. Therefore, a short-term experimental work was undertaken to assess potential risks due to weed seed contamination and determine the agronomic response of ryegrass (Lolium perenne L.) to soil incorporation of paunch. The risk of weed contamination from soil application of paunch appeared to be low; however, methods that account for viability of seeds may be required to fully discard such a risk. Soil application of paunch at field equivalent rates of 150-300 kg ha-1 of N increased dry matter yield by ≈30% on average compared with untreated grass, but was approximately 35% lower than a mineral fertilizer treatment applied at the same rates. Dry matter yield of paunch-treated grass was between 2000 and 3000 kg per ha over four consecutive cuts at 25-day intervals. Nitrogen use-efficiency of paunch was approximately 10% (range: 3% to 20%, depending on paunch type), and total N in harvested plant material showed values, which were between 2% and 3%. Overall, there appears to be potential for paunch-derived products to be used as a source of carbon and nutrients in crop production. Areas that merit a research priority within this space are also outlined in this paper. Such work is required to inform soil-, climate- and crop-specific land application rates, optimize agronomic performance, and minimize environmental concerns. There is also a requirement for the value proposition to industry to be determined, including reduced cost of disposal of material via gate fees and fertilizer replacement value

A comparison of rehabilitated coal mine soil and unmined soil supporting grazed pastures in south-east Queensland

Land that is disturbed by mining activities is required to undergo suitable rehabilitation. This study compared soils supporting grazed pasture on land that was rehabilitated after coal mining activity with that on unmined land. Pasture biomass, and soil physical and chemical properties important for pasture production and sustainability were intensively monitored on three sites that had completed rehabilitation at different times over the last 10 years, and one unmined control site. A further 18 unmined grazing sites were monitored for benchmarking purposes. Analysis of soil properties of plant available phosphorus and nitrogen, salinity and sodicity in the first year of the study suggested little difference in terms of benefits or constraints to pasture production between the rehabilitated and control sites. Plant-available phosphorus was sufficiently high in the two oldest rehabilitated sites that a fertiliser response would not be expected. Soil depth and the pasture rooting depth at the rehabilitated sites were at the shallow end of the wide range observed across the benchmark and control sites. Higher pasture biomass at the rehabilitated sites compared with the control at the initiation of the trial was attributed more to differences in grazing history than differences in soil attributes

Alternative energy sources for cotton production in Australia

Agriculture requires energy as an important input. Within highly mechanised agricultural productions systems such as the Australian cotton industry, energy inputs represent a significant cost to growers. In this paper, current uses of alternative energies, grower interest and perceptions of alternative energies and obstacles and opportunities are surveyed. The potential of traditional and alternative energy supply for agriculture and cotton production in Australia is also evaluated. It is found that in the cotton growing regions of Australia, the preferred alternative energy sources may be solar or bioenergy, rather than wind energy. The potential of biofuels and bioenergy production from cotton by-products such as cotton trashes and cotton seed oil is also examined