Nutritient flow scenarios for sustainable smallholder faming systems in southwestern Burkino Faso : food security and better livelihoods for rural dryland communities

The report presents a study on nutrient flows of agricultural livelihood systems dominated by smallholder farms in South-western Burkina Faso. The material flow analysis of nitrogen, phosphorus, and potassium provides a detailed picture of current nutrient flows within, in to, and out of smallholder farms. Such a picture allows quantifying material potentials for sustainable intensification, that is, increasing the ratio of crop yield to mineral fertilizer inputs. Finally, in the pursuit of indicators for sustainable intensification, we propose combining indicators derived from material flow analysis with indicators of socio-economic nature to move from material potential assessments to sustainability assessments. The combination is informed by the criticality concept, a concept which denotes how important a specific material resource is to an anthropogenic system. Based on an existing criticality determination methodology for metals, we sketch the criticality indicator set for the case of nitrogen, phosphorus, and potassium and smallholder farms. Further research should include increasing temporal boundaries to capture cycles longer than a year, the applied temporal boundary in this study. A multi-scale study including villages and landscapes could provide additional insights on the role of water bodies or future .industrial activities in nutrient cycling. In turn, the multi-scale MFAs would provide the necessary indicator values to assess nutrient criticality not only at the smallholder farm level, but also at the village and landscape level. Finally, the material flows could be further characterized with respect to gender, cost/benefits, etc

The nitrogen and phosphorus budget of Flanders: a tool for efficient waste management and nutrient recovery

The region of Flanders in Belgium is, due to its high population density, intensive industry and livestock production, a nutrient-rich region. This results in important anthropogenic emissions to the environment, but also a large potential for the recovery and reuse of nitrogen (N ) and phosphorus (P) from waste streams. In this study, a substance flow analysis study for N and P is presented, in which the anthropogenic fluxes, stocks and hot spots of these two nutrients are quantified throughout the Flemish economy and environment. The environmental impact of the different economic sectors is addressed through the determination of the N and P footprint. The importance of food production in the nutrient cycle is thereby demonstrated through the large contribution of agriculture to the nutrient footprint (49% of N and 36% of P). Further focus is placed on the nutrient use efficiencies across the different sectors of the food supply nexus to target key nutrient losses and inefficiencies. This leads to an overall fertilizer-to-consumer efficiency of 14% for N and P, with the main nutrient losses originating from livestock production and food processing. At the end of the production and consumption chain, important nutrient quantities are embedded in concentrated waste streams such as excess manure, food processing waste streams and activated sludge. This demonstrates the large potential for nutrient recovery as a tool to improve nutrient use efficiencies and reduce the dependency of inorganic fertilizers. Several nutrient recovery strategies, both physicochemical and microbial, were evaluated for their economic feasibility and their impact on the primary energy demand of the total food supply chain

Multiphase modelling of the effect of fluid shear stress on cell yield and distribution in a hollow fibre membrane bioreactor

We present a simplified two-dimensional model of fluid flow, nutrient transport and cell distribution in a hollow fibre membrane bioreactor, with the aim of exploring how fluid flow can be used to control the distribution and yield of a cell population which is sensitive to both fluid shear stress and nutrient concentration. The cells are seeded in a scaffold in a layer on top of the hollow fibre, only partially occupying the extracapillary space. Above this layer is a region of free-flowing fluid which we refer to as the upper fluid layer. The flow in the lumen and upper fluid layer is described by the Stokes equations, whilst the flow in the porous fibre membrane is assumed to follow Darcy’s law. Porous mixture theory is used to model the dynamics of and interactions between the cells, scaffold and fluid in the cell–scaffold construct. The concentration of a limiting nutrient (e.g. oxygen) is governed by an advection–reaction–diffusion equation in each region. Through exploitation of the small aspect ratio of each region and asymptotic analysis, we derive a coupled system of partial differential equations for the cell volume fraction and nutrient concentration. We use this model to investigate the effect of mechanotransduction on the distribution and yield of the cell population, by considering cases in which cell proliferation is either enhanced or limited by fluid shear stress and by varying experimentally controllable parameters such as flow rate and cell–scaffold construct thickness

Comparison of bacterioneuston and bacterioplankton dynamics during a phytoplankton bloom in a fjord mesocosm

The bacterioneuston is the community of Bacteria present in surface microlayers, the thin surface film that forms the interface between aquatic environments and the atmosphere. In this study we compared bacterial cell abundance and bacterial community structure of the bacterioneuston and the bacterioplankton (from the subsurface water column) during a phytoplankton bloom mesocosm experiment. Bacterial cell abundance, determined by flow cytometry, followed a typical bacterioplankton response to a phytoplankton bloom, with Synechococcus and high nucleic acid (HNA) bacterial cell numbers initially falling, probably due to selective protist grazing. Subsequently HNA and low nucleic acid (LNA) bacterial cells increased in abundance but Synechococcus did not. There was no significant difference between bacterioneuston and bacterioplankton cell abundances during the experiment. Conversely, distinct and consistent differences between the bacterioneuston and the bacterioplankton community structure were observed. This was monitored simultaneously by Bacteria 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE). The conserved patterns of community structure observed in all of the mesocosms indicate that the bacterioneuston is distinctive and non-random

Relationships between land use and nitrogen and phosphorus in New Zealand lakes

Developing policies to address lake eutrophication requires an understanding of the relative contribution of different nutrient sources and of how lake and catchment characteristics interact to mediate the source–receptor pathway. We analysed total nitrogen (TN) and total phosphorus (TP) data for 101 New Zealand lakes and related these to land use and edaphic sources of phosphorus (P). We then analysed a sub-sample of lakes in agricultural catchments to investigate how lake and catchment variables influence the relationship between land use and in-lake nutrients. Following correction for the effect of co-variation amongst predictor variables, high producing grassland (intensive pasture) was the best predictor of TN and TP, accounting for 38.6% and 41.0% of variation, respectively. Exotic forestry and urban area accounted for a further 18.8% and 3.6% of variation in TP and TN, respectively. Soil P (representing naturally-occurring edaphic P) was negatively correlated with TP, owing to the confounding effect of pastoral land use. Lake and catchment morphology (zmax and lake : catchment area) and catchment connectivity (lake order) mediated the relationship between intensive pasture and in-lake nutrients. Mitigating eutrophication in New Zealand lakes requires action to reduce nutrient export from intensive pasture and quantifying P export from plantation forestry requires further consideration

Spatially resolved monthly riverine fluxes of oxidised nitrogen (nitrate and nitrite) to the European shelf seas, 1960-2005

This report documents the methodology developed for statistically modelling the spatial and temporal patterns of oxidised nitrogen (nitrate plus nitrite) riverine fluxes into the coastal waters of northwestern Europe, over the period 1960-2005. The purpose of the study was to provide boundary data for a modelling study of new primary production in European waters. For the UK and Ireland, monthly freshwater discharges to a set of grid cells around the coastline were modelled from rainfall data and calibrated from detailed analyses performed for a subset of years with contrasting climatology. The mean and long-term trends in nitrate and nitrite content of the river discharges were modelled from Harmonised Monitoring Scheme data and flux estimates for each of the years of contrasting climateology. The product of the discharge rate and nitrogen content provided estimates of the monthly flux to each grid cell. Scandinavian inputs of nitrate and nitrite to the North Sea, Skagerrak and Kattegat were assembled from a composite of statistically modelled freshwater discharge, and recent estimates of nitrogen flux from national monitoring agencies. Fluxes of nitrate and nitrite from the rivers flowing into the North Sea from Germany, Netherlands and Belgium during 1960-2005 were assembled from previous analyses by researchers at the University of Hamburg. Nitrate and nitrite fluxes from French rivers flowing into the English Channel, in particular the Seine, were indirectly derived by correlation with the River Scheldt, calibrated from published estimates of annual fluxes. The results show the total oxidised nitrogen input to European shelf seas increasing from approximately 0.6Mt pa. in the 1960's to 1.2Mt pa. in the mid-1980's. Recent estimates of the annual flux since 2000 have been approximately 1.1Mt pa. Around 60-70% of the total annual flux to the northwest European shelf enters via the North Sea. Winter input rates are approximately twice those in the summer in all areas except the Skagerrak/Kattegat

Dry anaerobic digestion of organic residues on-farm - a feasibility study

Objectives The feasibility study shall answer the following questions: Are there economical and ecological advantages of on-farm dry digestion biogas plants? How the construction and operation parameters of a dry digestion biogas plant influence environment, profit, and sustainability of on-farm biogas production? The aim of the feasibility study is to provide facts and figures for decision makers in Finland to support the development of the economically and environmentally most promising biogas technology on-farm. The results may encourage on-farm biogas plant manufacturers to develop and market dry anaerobic digestion technology as a complementary technology. This technology may be a competitive alternative for farms using a dry manure chain or even for stockless farms. Results Up to now farm scale dry digestion technology does not offer competitive advantages in biogas production compared to slurry based technology as far as only energy production is concerned. However, the results give an over-view of existing technical solutions of farm-scale dry digestion plants. The results also show that the ideal technical solution is not invented yet. This may be a challenge for farmers and entrepreneurs interested in planning and developing future dry digestion biogas plants on-farm. Development of new dry digestion prototype plants requires appropriate compensation for environmental benefits like closed energy and nutrient circles to improve the economy of biogas production. The prototype in Järna meets the objectives of the project since beside energy a new compost product from the solid fraction was generated. On the other hand the two-phase process consumes much energy and the investment costs are high (>2000 € m-3 reactor volume). Dry digestion on-farm offers the following advantages: Good process stability and reliability, no problems like foam or sedimentation, cheap modules for batch reactors, less reactor capacity, reduced transport costs due to reduced mass transfer in respect of the produced biogas quantity per mass unit, compost of solid digestion residues suitable as fertiliser also outside the farm gate, use of on-farm available technology for filling and discharging the reactor, less process energy for heating because of reduced reactor size, no process energy for stirring, reduced odour emissions, reduced nutrient run off during storage and distribution of residues because there is no liquid mass transfer, suitable for farms using deep litter systems. These advantages are compensated by following constraints: Up to 50% of digestion residues are needed as inoculation material (cattle manure does not need inoculation) requiring more reactor capacity and mixing facilities. Retention time of dry digestion is up to three times longer compared to wet digestion requiring more reactor capacity and more process energy, filling and discharging batch reactors is time and energy consuming. We conclude that only farm specific conditions may be in favour for dry digestion technology. Generally, four factors decide about the economy of biogas production on-farm: Income from waste disposal services, compensation for reduction of greenhouse gas emission, compensation for energy production and - most important for sustainable agriculture - nutrient recycling benefits. Evaluation of the results We did not find any refereed scientific paper that includes a documentation of an on-farm dry digestion biogas plant. It seems that we tried first. We also could not find any results about the biogas potential of oat husks, so we may have found these results first. Farm scale production of anaerobically treated solid manure for composting is new. Dry fermentation biogas plants offer the possibility to design solid manure compost by variation of fermentation process parameters. From different scientific publication databases we found about 10 000 references concerning biogas research during the past 10 years. Less than ten are dealing with biogas reactors for non-liquid substrates on-farm. Recent research mainly concentrates on basic research, biogas process research for communal waste, large-scale biogas plants, and research on laboratory level. This mirrors the fact, that production of research papers is rather financed than product development on site. Our conclusion is that it seems worldwide to be very difficult or even impossible to find financial support for on site research, especially for on-farm prototype biogas reactors. We suppose the following reasons for this fact: biogas plant research requires proficiency in many different scientific disciplines, lack of co-operation between engineering and life sciences, high development costs to transfer basic research results into practical technical solutions, low interest of researchers because on site and on-farm research enjoys low appreciation in terms of scientific credits, portability of farm specific design and process solutions is difficult. Our conclusion is that on site and on-farm research has to be supported by funding agencies if integration of biogas and bio energy into the farm organism is considered as an important target within the agricultural policy framework. Future research on both dry fermentation technique and biogas yield of solid organic residues may close present knowledge gaps. Prototype research may offer competitive alternatives to wet fermentation for farms using a solid manure chain and/or energy crops for biogas production. To encourage farmers and entrepreneurs to foster the development of dry fermentation technology support in terms of education and advisory services is also necessary