Frank Brentrup

Methods to estimate on-field nitrogen emissions from crop production as an input to LCA studies in the agricultural sector

Nitrogen compounds emitted from the field are usually considered in Life Cycle Assessments (LCA) of agricultural products or processes. The environmentally most important of these N emissions are ammonia (NH3), nitrous oxide (N20) and nitrate (N03). The emission rates are variable due to the influence of soil type, climatic conditions and agricultural management practices. Due to considerable financial and time efforts, and great variations in the results, actual measurements of emissions are neither practical nor appropriate for LCA purposes. Instead of measurements, structured methods can be used to estimate average emission rates. Another possibility is the use of values derived from the literature which would, however, require considerable effort compared to estimation methods, especially because the values might only be valid for the particular system under investigation.In this paper methods to determine estimates for NH3, N20 and NO3 emissions were selected from a literature review. Different procedures were chosen to estimate NH3 emissions from organic (Horlacher &Marschner, 1990) and mineral fertilizers (ECETOC, 1994). To calculate the N2O emissions, a function derived by Bouwman (1995) was selected. A method developed by the German Soil Science Association (DBG, 1992) was adopted to determine potential NO3 emissions. None of the methods are computer-based and consequently require only a minimum set of input data. This makes them, on the one hand, transparent and easy to perform, while, on the other hand, they certainly simplify the complex processes.

Environmental impact assessment of agricultural production systems using the life cycle assessment methodology: I. Theoretical concept of a LCA method tailored to crop production

Abstract A new life cycle assessment (LCA) method is presented, which is specifically tailored to plant nutrition in arable crop production. Generally, LCA is a methodology to assess all environmental impacts associated with a product or a process by accounting and evaluating its resource consumption and emissions. In LCA studies the entire production system should be considered, i.e. for crop production systems the analysis includes not only the on-field activities, but also all impacts related to the production of raw materials (minerals, fossil fuels) and farm inputs like fertilizers, plant protection substances, machinery or seeds. The LCA method developed in this study evaluates the impact of emissions and resource consumption associated with crop production on the following environmental effects: depletion of abiotic resources, land use, climate change, toxicity, acidification, and eutrophication. In order to enable conclusions on the overall environmental impact of alternative crop nutrition systems, an aggregation procedure to calculate indicators for resource depletion (RDI) and environmental impacts (EcoX) has been developed. The higher the EcoX value, the higher is the overall environmental burden associated with the product under investigation. An environmental analysis of arable crop production systems based on this LCA method is especially appropriate in order to: (1) detect environmental hot spots in the system; (2) trace back environmental impacts of arable farming products to their sources and on that basis to suggest options for improvement; and (3) contribute to the debate on the environmental preference of alternative cropping systems in an informed way.

Environmental impact assessment of agricultural production systems using the life cycle assessment (LCA) methodology II. The application to N fertilizer use in winter wheat production systems

Abstract This study examined the environmental impact of different nitrogen (N) fertilizer rates in winter wheat production by using a new life cycle assessment (LCA) method, which was specifically tailored to crop production. The wheat production system studied was designed according to “good agricultural practice”. Information on crop yield response to different N rates was taken from a long-term field trial in the UK (Broadbalk Experiment, Rothamsted). The analysis considered the entire system, which was required to produce 1 ton of wheat grain. It included the extraction of raw materials (e.g. fossil fuels, minerals), the production and transportation of farming inputs (e.g. fertilizers) and all agricultural operations in the field (e.g. tillage, harvest). In a first step, all emissions and the consumption of resources connected to the different processes were listed in a Life Cycle Inventory (LCI) and related to a common unit, which is 1 ton of grain. Next a Life Cycle Impact Assessment (LCIA) was done, in which the inventory data are aggregated into indicators for environmental effects, which included resource depletion, land use, climate change, toxicity, acidification, and eutrophication. After normalization and weighting of the indicator values it was possible to calculate summarizing indicators for resource depletion and environmental impacts (EcoX). At N rates of 48, 96, 144 or 192 kg N/ha the environmental indicator “EcoX” showed similar values per ton of grain (0.16–0.22 EcoX/ton of grain). At N rates of zero, 240 and 288 kg N/ha the EcoX values were 100–232% higher compared with the lowest figure at an N rate of 96 kg N/ha. At very low N rates, ‘land use’ was the key- environmental-factor, whereas at high N rates ‘eutrophication’ was the major problem. The results revealed that agronomical optimal arable farming does not necessarily come into conflict with economic and environmental boundary conditions.

Application of the Life Cycle Assessment methodology to agricultural production: an example of sugar beet production with different forms of nitrogen fertilisers

Abstract The suitability of the Life Cycle Assessment (LCA) methodology to analyse the environmental impact of agricultural production is investigated. The first part of an LCA is an inventory of all the resources used and emissions released due to the system under investigation. In the following step, i.e. the Life Cycle Impact Assessment the inventory data were analysed and aggregated in order to finally get one index representing the total environmental burden. For the Life Cycle Impact Assessment (LCIA) the Eco-indicator 95 method has been chosen, because this is a well-documented and regularly applied impact assessment method. The resulting index is called Eco-indicator value. The higher the Eco-indicator value the stronger is the total environmental impact of an analysed system. A sugar beet field experiment conducted in northeastern Germany was chosen as an example for the analysis. In this experiment three different nitrogen fertilisers (calcium ammonium nitrate=CAN, urea ammonium nitrate solution=UAN, urea) were used at optimum N rates. The obtained Eco-indicator values were clearly different for the N fertilisers used in the sugar beet trial. The highest value was observed for the system where urea was used as N source. The lowest Eco-indicator value has been calculated for the CAN system. The differences are mainly due to different ammonia volatilisation after application of the N fertilisers. For all the systems the environmental effects of acidification and eutrophication contributed most to the total Eco-indicator value. The results show that the LCA methodology is basically suitable to assess the environmental impact associated with agricultural production. A comparative analysis of the system, contribution to global warming, acidification, eutrophication and summer smog is possible. However, some important environmental issues are missing in the Eco-indicator 95 method (e.g. the use of resources and land).

Life Cycle Impact assessment of land use based on the hemeroby concept

The impact category ‘land use’ describes in the Life Cycle Assessment (LCA) methodology the environmental impacts of occupying, reshaping and managing land for human purposes. Land use can either be the long-term use of land (e.g. for arable farming) or changing the type of land use (e.g. from natural to urban area). The impact category ‘land use’ comprises those environmental consequences, which impact the environment due to the land use itself, for instance through the reduction of landscape elements, the planting of monocultures or artificial vegetation, or the sealing of surfaces. Important environmental consequences of land use are the decreasing availability of habitats and the decreasing diversity of wildlife species. The assessment of the environmental impacts of land use within LCA studies is the objective of this paper. Land use leads to a degradation of the naturalness of the area utilised. In this respect the naturalness of any area can be defined as the sum of land actually not influenced by humans and the remaining naturalness of land under use. To determine the remaining naturalness of land under use, this study suggests applying the Hemeroby concept. “Hemeroby is a measure for the human influence on ecosystems” (Kowarik 1999). The Hemeroby level of an area describes the intensity of land use and can therefore be used to characterise different types of land use. Characterization factors are proposed, which allow calculating the degradation of the naturalness of an area due to a specific type of land use. Since the resource ‘nature/naturalness’ is on a larger geographical scale by far not homogeneous, the assessment of land use needs to be regionalised. Therefore, the impact category ‘land use’ has been subdivided into the impact sub-categories ‘land use in European biogeographic regions’. Following the general LCA framework, normalization values for the impact sub-categories are calculated in order to facilitate the evaluation of the characterization results with regard to their share in a reference value. Weighting factors, which enable an aggregation of the results of the different land use sub-categories and make them comparable to other impact categories (e.g. climate change or acidification) are suggested based on the assumption that the current land use pattern in the European biogeographic regions is acceptable.

Impact assessment of abiotic resource consumption conceptual considerations

The impact assessment of the consumption of abiotic resources, such as fossil fuels or minerals, is usually part of the Life Cycle Impact Assessment (LCIA) in LCA studies. The problem with the consumption of such resources is their decreasing availability for future generations. In currently available LCA methods (e.g. Eco-indicator’ 99/Goedkoop and Spriensma 1999, CML/Guinée 2001), the consumption of various abiotic resources is aggregated into one summarizing indicator within the characterization phase of the LCIA. This neglects that many resources are used for different purposes and are not equivalent to each other. Therefore, the depletion of reserves of functionally non-equivalent resources should be treated as separate environmental problems, i.e. as separate impact sub-categories. Consequently, this study proposes assigning the consumption of abiotic resources to separate impact sub-categories and, if possible, integrating them into indicators only according to their primary function (e.g. coal, natural gas, oil → consumption of fossil fuels; phosphate rock → consumption of phosphate). Since this approach has been developed in the context of LCA studies on agricultural production systems, the impact assessment of the consumption of fossil fuels, phosphate rock, potash salt and lime is of particular interest and serves as an example. Following the general LCA framework (Consoli et al. 1993, ISO 1998), a normalization step is proposed separately for each of the subcategories. Finally, specific weighting factors have been calculated for the sub-categories based on the ’distance-to-target’ principle. The weighting step allows for further interpretation and enables the aggregation of the consumption of different abiotic resources to one summarizing indicator, called the Resource Depletion Index (RDI). The proposed method has been applied to a wheat production system in order to illustrate the conceptual considerations and to compare the approach to an established impact assessment method for abiotic resources (CML method, Guinée 2001).

Direct Nitrous Oxide Emissions From Tropical And Sub-Tropical Agricultural Systems: A Review and Modelling of Emission Factors

There has been much debate about the uncertainties associated with the estimation of direct and indirect agricultural nitrous oxide (N2O) emissions in developing countries and in particular from tropical regions. In this study, we report an up-to-date review of the information published in peer-review journals on direct N2O emissions from agricultural systems in tropical and sub-tropical regions. We statistically analyze net-N2O-N emissions to estimate tropic-specific annual N2O emission factors (N2O-EFs) using a Generalized Additive Mixed Model (GAMM) which allowed the effects of multiple covariates to be modelled as linear or smooth non-linear continuous functions. Overall the mean N2O-EF was 1.2% for the tropics and sub-tropics, thus within the uncertainty range of IPCC-EF. On a regional basis, mean N2O-EFs were 1.4% for Africa, 1.1%, for Asia, 0.9% for Australia and 1.3% for Central & South America. Our annual N2O-EFs, estimated for a range of fertiliser rates using the available data, do not support recent studies hypothesising non-linear increase N2O-EFs as a function of applied N. Our findings highlight that in reporting annual N2O emissions and estimating N2O-EFs, particular attention should be paid in modelling the effect of study length on response of N2O.

Sustainable Intensification of Maize and Rice in Smallholder Farming Systems Under Climate Change in Tanzania

Maize and rice are major staple food crops in Tanzania and constitute 31 % and 13 %, respectively, of total food production. The current productivity of the two crops (1.6 t/ha and 2.3 t/ha, respectively) will not match with the increasing demand for food created by population growth unless there is an expansion of cultivated land or intensification measures are imparted to smallholder farmers, who produce nearly 90 % of each crop in the country. Expansion of cropped areas is limited by increased land-use pressure. Under smallholder farming the same land is continuously cultivated without proper input to replenish the removal of nutrients with crop harvesting, which leads to a decline in the subsequent crop yield. The situation is exacerbated by the effects of climate change. The smallholder farmers lack agro-inputs, information and extension services, and are faced with erratic rainfall. Therefore, a public-private partnership comprising two public universities and two multinational companies dealing with fertilizer and crop protection was initiated in December 2010, aiming at demonstrating sustainable intensification of maize and rice production in smallholder farmers’ fields. Five farms for maize and four for rice crops in different villages and districts were selected, and their soils were sampled for physical and chemical analysis. Two treatments were imposed on each farm. The treatments were farmers’ practice (control) and improved practice, which includes the proper use of fertilizer, crop protection inputs and recommended crop seed variety. Generally, the soils of most farms were acidic with low phosphorus, potassium, magnesium, sulphur, copper and zinc values. On average, maize and rice grain yield 14 % moisture content ranged from 2.5 to 5.4 t/ha in farmers’ practice and 6.6–8.5 t/ha in improved practice. Maize and rice stover/straw biomass ranged from 5.33 to 15.4 t/ha for improved practice and 2.11–9.13 t/ha for farmers’ practice. It can be concluded that improved agricultural practices, including plant nutrition, plant protection, improved seeds and conservation agriculture measures (e.g., crop residue recycling), enable sustainable intensification of smallholder crop production. Crop yields are improved, soil fertility is maintained, and family income is increased all at the same time. Therefore, public-private partnerships are needed to put this concept into practice and to make knowledge and technology available to smallholder farmers.

Life cycle assessment of crop production

The “environmental footprint” of crop production includes a wide range of different impacts such as nitrate leaching, ammonia volatilization, greenhouse gas emissions, or energy consumption, which itself may contribute to different environmental effects such as eutrophication, acidification, and global warming. The life cycle assessment (LCA) methodology is particularly suitable to examine and analyze the “environmental footprint,” because LCA is an inventory and evaluation of all environmental impacts (emissions and resource consumption) along the life cycle of a product from “cradle to grave.” For fertilizer, this means the inclusion of raw material extraction, through production to application. Today, LCA is a standardized methodology that is mainly used to compare different alternatives (products or services) and to determine their environmental hot spots.

Application of the life cycle assessment methodology to investigate the environmental impact of different nitrogen fertiliser application rates in a crop rotation

In this study the environmental impact of a reduced (Nopt-40%) and an optimum (Nopt) N fertilisation in a crop rotation is investigated using the Life Cycle Assessment (LCA) methodology. This method allows for an inventory and evaluation of all environmental impacts associated with the entire crop production system inclusive of all pre-chain processes. The study is based on a long-term field trial with cereals and maize. The study reveals that the Nopt-40% fertilisation is preferable to the Nopt fertilisation concerning climate change, human toxicity, acidification and eutrophication. On the other hand the Nopt application rate shows lower indicator values for abiotic resource depletion, land use, ecotoxicity and formation of photo-oxidants. It can be concluded that none of the compared N fertiliser regimes is clearly preferable from an environmental point of view. To determine a distinct environmentally optimum N application rate, it is first necessary to identify an environmental indicator that summarises all environmental effects.