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Agronomic and environmental impacts of organic materials applied to agricultural land - WQ0206

A consortium of personnel from WRc and AEA, with specific technical input from Professor Nortcliff at the University of Reading, has been assembled to complete this project. The consortia provides technical expertise for the full range of scientific skills that are required to successfully complete the project and ensure the objectives laid out in the tender brief can be fully met.

The recycling of organic materials to agricultural land is one of the longest established forms of waste recycling, and has played a valuable role in agriculture for thousands of years. Organic materials can provide many benefits, including adding valuable nutrients, improving soil structure and water holding capacity, beneficially altering the pH of the soil and increasing organic content. When managed well, these activities can result in increased crop yield and quality, and reduce the amount of chemical fertilisers required by the crop.

The spreading of organic wastes however is not without risk. Poor management, such as the spreading of these materials at inappropriate times, or in quantities in excess of crop needs, can lead to a build up of heavy metal contamination in the soil, and leaching of nutrients to rivers and groundwater. Increased emissions of greenhouse gases such as carbon dioxide, methane and nitrous oxide are also associated with waste spread to land where the spreading is not well managed or controlled. Agriculture accounts for two thirds of the UK's emissions of nitrous oxide and 40 per cent of methane emissions, demonstrating the importance of appropriate management in dealing with waste to land. The Environment Agency have had cause to prosecute 44 companies and individuals involved in waste to land activities since 2005, illustrating that good practice is not universally observed. Levels of nitrates and phosphates in inland waters, which can have detrimental impacts on bio-diversity, continue to decline but the main source of these nutrients is still run-off from agricultural land.
This study will investigate the benefit and impact of a wide range of organic materials. The scope will include both materials that have been applied to land for many years and are relatively well understood, such as manures and sewage sludges, and the new generation of wastes from modern waste treatment technologies, such as anaerobic digestates and compost from the mechanical and biological treatment (MBT) of municipal waste. Anaerobic digestion is currently widely deployed in the water industry, but is relatively new to the waste industry in this country. The success of these modern treatment technologies is vital for the UK to succeed in meeting its targets for diverting waste from landfill and reducing greenhouse gas emissions and to ensure this happens environmental impacts of outputs from these technologies must be well understood.

The nutrient content of the organic materials crucial to successful agronomy will be examined, as well as detrimental characteristics of the materials, such as heavy metal contamination (mercury, lead etc), the adverse effects of which on the environment are well documented. The study will also pull together previous work on pathogens, and the potential of organic materials to increase the risk of pathogens spreading disease in humans, animals and plants. The investigation will look at similarities and differences between materials new to the agricultural sector and established wastes (such as residues from anaerobic digestion of sewage sludge compared to residues from anaerobic digestion of municipal waste or livestock manures). The investigation will look at the impact on various environmental compartments, including air, soil, ground and surface water, and uptake by crops.

This project will initially review currently available data (both nationally and internationally) on wastes spread to land, including nutrient and heavy metal content of the materials, and assessment of the quality of the data. Studies recently completed by the consortium, such as the review of wastes spread to land as part of the exemption review for Defra, and the environmental impacts of sewage sludge spread to land for the European Commission, will be used in this project as an important source of data held in-house by the consortia.

The second phase of the project will assess the relative merits of the different materials, where synergies exist between new and more established wastes, and establish what further data is necessary to ensure that safe and efficient recycling of organic materials to land can continue.
7. (b) Objectives

There has been a substantial amount of research on the benefits and impacts of spreading organic materials to agricultural land in the last decade. For some materials, such as sewage sludge, a large amount of characterisation data exists which is linked to the benefits and environmental impact of this material when recycled to land. The benefits and disbenefits of other materials, such as composts and anaerobic digestates derived from source segregated organic wastes, and untreated wastes spread under the current exemption regime are less well understood, but a significant body of evidence is available on the primary characteristics of such wastes from which to draw conclusions.
Implementation of several legislative and policy instruments is expected to significantly change the quality and quantity of organic wastes recycled to land for agricultural benefit. Examples of these drivers for change include:

• Waste Strategy for England;
• The Landfill Directive;
• Animal By-products Order;
• Renewables Obligation Order
• The Climate Change Act 2008; and
• Proposed changes to The Environmental Permitting Regulations for exemptions for spreading wastes to agricultural land

As the UK endeavours to meet its obligations for renewable sources of energy, reduction of greenhouse gases (GHG) and meet landfill diversion targets, the treatment of organic wastes and the types and characteristics of such treated wastes applied to agricultural soils may change significantly. Many more organic wastes may be recycled to land, most of which will be from disparate sources and will have undergone some form of pre-treatment (principally either composting or anaerobic digestion). For example, currently only about 0.1% of livestock manures are treated by anaerobic digestion at 20 on-farm systems. There is therefore huge potential for growth in this sector as a means to produce renewable energy, but at the same time generating manure derived anaerobic digestates. The organic wastes going to land in the future may in part substitute for many wastes historically recycled to land which have had little biological pre-treatment such as lime treated and heat dried sewage sludge and paper waste sludges, as well as increase in the total volume of organic wastes recycled to soil. Where these new wastes have an agronomic benefit, an obvious reuse route would be application to agricultural land. This would inevitably have implications for land bank available to accept these materials.
The impact of large scale changes in the quantities and diverse nature of organic wastes being recycled to soil needs to be carefully considered. Soil is a complex medium and its ability to maintain ecological processes, functions, biodiversity and productivity into the future is key to a sustainable future. A key rational for recycling organic wastes to land is to supply nutrients for crop plant growth which reduce the need for producing inorganic fertilisers that require large amounts of energy to produce. The organic matter contained within the wastes may also provide other soil improving properties such as better soil structure and water holding properties, reducing erosion and drought problems.

Defra wish to let a contract to review the agronomic and environmental impacts of a diverse range of organic wastes to agricultural land. They have identified five specific objectives in the tender brief which they require a better understanding of to guide policy decisions in this area:

1. To provide an assessment of the pollution risk, greenhouse gas emissions and agronomic benefits from a range of organic materials recycled to land.
2. To recommend future research needed to develop guidelines and to assess trade-offs between nutrient recycling, losses to water and losses to air.
3. To recommend changes to guidelines for application to land of the above materials if applicable.
4. To recommend suitable rates of application of anaerobic digestate to land, in order to optimise GHG mitigation of the process while recovering nutrients.
5. To provide a short executive summary for policy makers.
Using the combined knowledge and contacts of experts from WRc, AEA, and the Soil Science Department at the University of Reading, the consortium would collate and assess existing data from many disparate sources. Conclusions would then be drawn on the impacts and benefits of a range of organic materials which are well founded, accurate and constructive. Where gaps exist in the science base these will be clearly identified. By efficiently managing and carrying out the data collection and interpretation exercise, the consortium would meet the requirements set out in the tender specification.
In a four month contract it is not possible to generate significant quantities of new testing data and the data collection exercise required to complete this project would therefore be limited to secondary research of existing information. The review will need to take in a large body of data in the first stages of the project to achieve this, a team of nationally recognised experts has been assembled which already has access to much of the available data. This approach offers a considerable saving of time and costs to the project.
In order to complete the overall objectives of the project the consortium would complete a series of tasks which are detailed below. The activities and flow of work required to complete these tasks are summarised in the flow chart provided in Figure 1. The flow chart identifies which organisation would take the lead in delivery of identified work items. The tasks to be completed are:
Task 1) Project scoping activities. (Milestone 1).
Task 2) Identify and collate data from sources identified in Task 1.
Task 3) Design database for all possible wastes and data identified in Task 1, by environmental compartment as identified in the project brief. Populate database and produce a proposed Report Structure for Defra review. (Milestone 2).
Task 4) Review the quality of the collated data (i.e. limits of detection; quality of sampling; sources of data etc.) and undertake amendments to the database where required. This activity would include an assessment of potential data gaps. (Milestone 3).
Task 5) Develop assessment framework to assess short and long term risk and benefits of individual waste types. (Milestone 4).
Task 6) Undertake evaluation of identified organic materials using the agreed assessment methodology.
Task 7) Produce initial draft report with findings and recommendations for comment from Defra representatives (Milestone 5).
Task 8) Undertake holistic assessment activities to produce final review, including non-technical summary and articles for publication (Milestone 6)

Where possible many of the above tasks would be run concurrently in order to meet the tight deadlines imposed on the project (see the GANTT chart in Figure 2 for further details).
Project Documents
• FRP - Final Report : Defra agron assmt sid5   (298k)
• ANX - Annex : DEFRA8021 Appendix A   (1868k)
• ANX - Annex : DEFRA8021 Appendix B   (302k)
• ROAME Document : WQ01   (200k)
Time-Scale and Cost
From: 2009

To: 2009

Cost: £39,963
Contractor / Funded Organisations
WRc plc
Environmental Protection              
Sustainable Farming and Food              
Sustainable Farming and Food Science              
Water Quality              
Water Quality and Use