Variation in carbon footprint of milk due to management differences between Swedish dairy farms

To identify mitigation options to reduce greenhouse gas (GHG) emissions from milk production (i.e. the carbon footprint (CF) of milk), this study examined the variation in GHG emissions among dairy farms using data from previous CF studies on Swedish milk. Variation between farms in these production data, which were found to have a strong influence on milk CF were obtained from existing databases of e.g. 1051 dairy farms in Sweden in 2005. Monte Carlo analysis was used to analyse the impact of variations in seven important parameters on milk CF concerning milk yield (energy corrected milk (ECM) produced and delivered), feed dry matter intake (DMI), enteric methane emissions, N content in feed DMI, N-fertiliser rate and diesel used on farm. The largest between farm variation among the analysed production data were N-fertiliser rate (kg/ha) and diesel used (l/ha) on farm (coefficient of variation (CV) 31-38%). For the parameters concerning milk yield and feed DMI the CV was approx. 11 and 8%, respectively. The smallest variation in production data was found for N content in feed DMI. According to the Monte Carlo analysis, these variations in production data led to a variation in milk CF of between 0.94 and 1.33 kg CO2 equivalents (CO2e) per kg ECM, with an average value of 1.13 kg/CO2e kg ECM. We consider that this variation of ±17% that was found based on the used farm data would be even greater if all Swedish dairy farms were included, as the sample of farms in this study was not totally unbiased. The variation identified in milk CF indicates that a potential exists to reduce GHG emissions from milk production on both national and farm level through changes in management. As milk yield and feed DMI are two of the most influential parameters for milk CF, feed conversion efficiency (i.e. units ECM produced per unit DMI) can be used as a rough key performance indicator for predicting CF reductions. However, it must be borne in mind that feeds have different CF due to where and how they are produced

Nitrate leaching and spring wheat bread making quality following cultivation of grasslands of different composition, age and management

The influence of sward botanical composition and ley age on grassland residual effects, quality of spring wheat and subsequent nitrate leaching was investigated. Grazed grasslands of different age (1, 2 and 8 production years) and composition (unfertilised grass-clover and fertilised perennial ryegrass) were ploughed and followed by spring wheat and spring barley. For reference, an adjacent field without grassland history but with the same crop sequence in 2002-2003 was treated with increasing quantities of N fertiliser. Yields and N uptake of spring wheat following grasslands always exceeded those of the reference plots with a history of cereal production. The nitrogen fertiliser replacement values of grass-clover and ryegrass were 59-100 and 72-121 kg ha-1, respectively, with the highest values representing the 8-year-old leys. Grain yield and N uptake increased while those for straw decreased with increasing ley age. There were no effects of previous grassland type (grass-clover/ryegrass) on content of protein, starch and gluten, but grassland age significantly influenced protein (P<0.05) and gluten (P<0.01) contents. It is suggested that N mineralisation following the ploughing of older grass leys occurred later than when following the 1st year ley. The protein and gluten contents of wheat following unfertilised grass-clover corresponded to those following cereals given 125-150 kg N ha-1, but the rheological properties of the gluten were different to what could be achieved using equivalent quantities of mineral fertiliser. Probably, the slow release of N from decomposition of old grassland gave a better synchrony between N release and plant demand. Nitrate leaching in year 1 after ploughing was significantly influenced by type of grassland (P<0.001) with 10 and 29 kg N ha-1 leached from grass-clover and ryegrass, respectively. Nitrate leaching following ploughing of 1-year-old leys averaged 11 kg N ha-1 which was significantly lower than the 24 kg N ha-1 following 2 or 8-year-old leys. The flow-weighted mean nitrate concentration decreased from 8.5 mg N l-1 in year 1 after grassland cultivation to 4.5 mg N l-1 in year 2. More N was released following ploughing of ryegrass swards and from grasslands of increasing age, but differences were moderate compared to the estimated N-surplus. This indicates that when organic matter in grasslands is partially decomposed and readily mineralisable N used, the remaining organic N is released only very slowly

Nutrient recovery from digestates : techniques and end-products

In nitrate vulnerable zones application of animal manure to land is limited. Digestate from anaerobic digestion plants competes with manure for nutrient disposal on arable land, which forms a serious hinder for the biogas sector to develop in these regions. Hence, one of its biggest challenges is to find cost-effective and sustainable ways for digestate processing or disposal. Furthermore, primary phosphorus resources are becoming scarce and expensive and will be depleted within a certain time. This urges the need to recycle P from secondary sources, like digestate or manure. From a sustainability point of view, it seems therefore no more than logical that digestate processing techniques switched their focus to nutrient recovery rather than nutrient removal. This paper gives an overview of digestate processing techniques, with a special focus on nutrient recovery techniques. In this paper nutrient recovery techniques are delineated as techniques that (1) create an end-product with higher nutrient concentrations than the raw digestate or (2) separate the envisaged nutrients from organic compounds that are undesirable in the end-product, with the aim to produce an end-product that is fit for use in chemical or fertiliser industry or as a mineral fertiliser replacement. Various nutrient recovery techniques are described, with attention for some technical bottlenecks and the current state of development. Where possible, physicochemical characteristics of the endproducts are given

Integration of on-farm biodiesel production with anaerobic digestion to maximise energy yield and greenhouse gas savings from process and farm residues

Anaerobic co-digestion of residues from the cold pressing and trans-esterification of oilseed rape (OSR) with other farm wastes was considered as a means of enhancing the sustainability of on-farm biodiesel production. The study verified the process energy yields using biochemical methane potential (BMP) tests and semi-continuous digestion trials. The results indicated that high proportions of OSR cake in the feedstock led to a decrease in volatile solids destruction and instability of the digestion process. Co-digestion with cattle slurry or with vegetable waste led to acceptable specific and volumetric methane productions, and a digestate low in potentially toxic elements (PTE). The results were used to evaluate energy balances and greenhouse gas emissions of the integrated process compared with biodiesel production alone. Co-digestion was shown to provide energy self-sufficiency and security of supply to farms, with sufficient surplus for export as fuel and electricit

Characterisation of dairy soiled water in a survey of 60 Irish dairy farms

peer-reviewedDairy farming in Ireland generates an effluent known as dairy soiled water (DSW), which consists of a relatively dilute mixture of cow faeces, urine, spilt milk and detergents that is typically applied to grassland. However, relatively little is known about the volumes generated, nutrient content and management factors that influence volume and concentration. Sixty dairy farms that had a separate storage tank for storing DSW were selected for this study. The spatial distribution of the farms reflected the spatial distribution of dairy cows across the 26 counties of the Republic of Ireland, with each farm representing between 10,000 and 20,000 dairy cows. Samples were analysed for biochemical oxygen demand (BOD), ammonium N (NH4-N), total nitrogen (TN), potassium (K), phosphorus (molybdate-reactive and total) (MRP and TP) and dry matter (DM) content. Management characteristics and parlour properties were quantified. Factors influencing volume and concentration of DSW were determined using mixed model multiple regression analysis. On average, 9784 l (standard error 209 l) of DSW, including rainfall, was produced cow−1 year−1 and this contained significant quantities of total N, P and K (587, 80 and 568 mg l−1, respectively). A typical Irish dairy farm stocked at 1.9 cows ha−1 could therefore supply approximately 13, 2 and 12 kg ha−1 of total N, P and K, respectively, across the farm, annually to meet some of the nutrient requirements for herbage production and potentially replace some of the synthetic fertilizer use. Seventy one percent of samples were within the regulated concentration limits of soiled water for BOD (<2500 mg l−1), rising to 87% during the closed period for slurry spreading (mid October to mid-late January), while 81% were within the concentration limits for DM (<1% DM), rising to 94% during the closed period. The efficiency of a milking parlour (cows per unit, time taken) plays a key role in determining the volume of DSW generated. This, in turn, also influences the concentration of nutrients and other chemicals. Large variability was found in nutrient concentrations and this presents a challenge for effective nutrient management to maximise the fertilizer replacement value of DSW

Combination of the Swiss agrarian sector model SILAS-dyn with the life cycle assessment tool SALCA

The agricultural sector model SILAS-dyn has been used by Agroscope ART for 10 years for the political advisory of the Swiss agricultural administration. To evaluate the environmental effects of different policy scenarios, a LCA module has been developed, connecting a hierarchical linkage to an existing LCA calculating tool. This lowers the formulation input and simplifies the adaptation of updated environmental models. The results of four scenarios show, through the example of energy use as an environmental impact, that indirect effects, such as energy use in the context of imported concentrates, can influence conclusions significantly. The scenario suggesting an increase of fertiliser prices does not change the results significantly, whereas higher energy prices increase the pressure upon energy-intensive activities.Sector model, LP, Political advisory, LCA, Income, Agricultural and Food Policy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,

Estimating the economic implications for grazing properties in the Mackay Whitsunday catchments of practice changes to more sustainable landscapes

In the Mackay Whitsunday region, the dominant grazing based operations are small intensive systems that heavily utilise soil, nutrient and chemical management practices. To improve water quality entering the Great Barrier Reef, graziers are being encouraged to adopt improved management practices. However, while there is good understanding of the management changes required to reach improved practice classification levels, there is poor understanding of the likely economic implications for a grazier seeking to move from a lower level classification to the higher level classifications. This paper provides analysis of the costs and benefits associated with adoption of intensive grazing best management practices to determine the effect on the profitability and economic sustainability of grazing enterprises, and the economic viability of capital investment to achieve best management. The results indicate that financial incentives are likely to be required to encourage smaller graziers to invest in changing their management practices, while larger graziers may only require incentives to balance the risk involved with the transition to better management practices.grazing, management practices, incentives, Mackay Whitsunday, Farm Management,

Evaluation of agri-environmental policies for water quality improvement accounting for firm heterogeneity

Policy makers worldwide are interested in the identification of cost-effective policy instruments to reduce diffuse pollution. A large economic model representing heterogeneous farms is used to evaluate a broad set of policies for reducing nitrate regulation within a large catchment dominated by dairy production. A policy instrument that allows the level of abatement to vary among producers according to differences in abatement cost is most cost-effective. The primary goal of 26 kg N ha⁻¹ can be achieved at a cost of $15 ha⁻¹ under this cap and trade policy, while a uniform cap on emissions for all farmers would be more than three times as expensive ($49 ha⁻¹). In contrast, requiring uniform reductions in stocking rate, banning the application of nitrogen fertiliser, and land retirement perform poorly. These instruments are at least three times more costly than a cap and trade policy over all simulated reductions. Moreover, the differentiated policy does not greatly alter the distribution of farm profit, relative to what exists without regulation. The use of a large, complex economic model incorporating disaggregated farms provides unique insight into the economic benefits accruing to a differentiated policy

Energetic and environmental benefits of co-digestion of food waste and cattle slurry: a preliminary assessment

The research evaluated the feasibility of centralised pre-processing and pasteurisation of source-separated domestic food waste followed by transport to farms for anaerobic co-digestion with dairy cattle slurry. Data from long-term experiments on the co-digestion of these two substrates was used to predict gross energy yields; net yields were then derived from full system analysis using an energy modelling tool. The ratio of cattle slurry to food waste in the co-digestion was based on the nutrient requirements of the dairy farm and was modelled using both nitrogen and phosphorous as the limiting factor. The model was run for both medium-size and large farms in which the cattle were housed either all year round or for only 50% of the year. The results showed that the addition of food waste improved energy yields per digester unit volume, with a corresponding increased potential for improving farm income by as much as 50%. Data for dairy farms in the county of Hampshire UK, which has a low density of dairy cattle and a large population, was used as a stringent test case to verify the applicability of the concept. In this particular case the nutrient requirements of the larger farms could be satisfied, and further benefits were gained from the reduction in greenhouse gas emissions avoided through improved manure management and fertiliser imports. The results indicated that this approach offered major advantages in terms of resource conservation and pollution abatement when compared to either centralised anaerobic digestion of food waste or energy recovery from thermal treatmen