«FARM SCALE BIOGAS AND COMPOSTING TO IMPROVE BATHING WATER QUALITY February 2006 Prepared for The Scottish Executive, Water Division by Greenfinch Ltd ...»
FARM SCALE BIOGAS AND COMPOSTING
TO IMPROVE BATHING WATER QUALITY
The Scottish Executive, Water Division
Greenfinch Ltd & Enviros Consulting Ltd
Michael Chesshire (Greenfinch Ltd) & John Ferry (Enviros Consulting Ltd)
1. PROJECT OVERVIEW
2. DESIGN AND OPERATION
3. PROJECT CATCHMENTS AND FARMS
4. ENVIRONMENTAL MONITORING
5. MODELLING THE EFFECT OF MANURE TREATMENT ON FIO
AND NUTRIENT FLUXES6. ECONOMIC ASSESSMENT
7. SUSTAINABILITY APPRAISAL
8. CONCLUSIONS AND RECOMMENDATIONS
ANNEX 1 – PROCUREMENT, CONTRUCTION AND COMMISSIONINGOF PLANTS
ANNEX 2 – CONCEPTUAL BASIS AND MODEL DEVELOPMENTANNEX 3 – ECONOMIC ASSESSMENT ANNEX 4 – SUSTAINABILITY TABLE
ANNEX 5 – FUTURE MONITORING SCHEDULEREFERENCES
FARM SCALE BIOGAS AND COMPOSTING TO IMPROVE BATHING WATER QUALITY
1. PROJECT OVERVIEW 1-1
1.1 Introduction 1-1
1.2 Project Objectives 1-1
1.3 Project Background 1-2
1.4 Previous Work 1-2
1.5 Research protocol 1-3
1.6 Project Methodologies 1-4
1.7 Formal Agreements 1-6
FARM SCALE BIOGAS AND COMPOSTING TO IMPROVE BATHING WATER QUALITY1. PROJECT OVERVIEW 1.1 Introduction A consortium comprising Greenfinch and Enviros was commissioned by the Scottish Executive Environment and Rural Affairs Dept. (SEERAD), in December 2003. The aim of the pilot project was for the provision of research, design, procurement and installation of pilot anaerobic digestion (AD) plants, (also known as biogas plants) and composting facilities (also known as aerobic composting or AC) in south west Scotland to minimise faecal indicator organism (FIO) pollution from agricultural sources to watercourses and bathing waters, especially during the bathing water season. A risk model was developed to provide a comprehensive evaluation of FIO pollution risk. The project also assessed, monitored and modelled the effect of AD and compost treatment on nutrient plant availability and soilleaching potential therefore addressing a broader range of diffuse pollution issues.
The design, procurement and installation of the AD plant were managed by Greenfinch, and the design, procurement and installation of the composting facilities were managed by Enviros. The contract management of the project was provided by Greenfinch, and the monitoring, modelling and research appraisal of the project was conducted by Enviros.
In total 10 plants were installed; 7 AD plants and 3 compost facilities on a total of 9 farms, with one farm having both an AD plant and composting facility. This report details the project in full, including plant design and installation, the findings of monitoring and research undertaken, economic and sustainability appraisals and the resulting conclusions and recommendations.
The aims of the project were to:
• Design, procure and install AD plants and compost facilities on study farms in the Saltcoats and Sandyhills catchments of South West Scotland; and,
• Design an environmental and FIO monitoring scheme that would:
There are 60 identified bathing waters in Scotland (Scotland’s Bathing Water Standards, 2002). The two pilot catchments bathing waters; Sandyhills (Dumfriesshire) and Saltcoats (Ayrshire), have been identified as areas at continued risk of failure of the European Bathing Waters Directive (76/160/EEC) mandatory standards for microbial water quality. Microbial pollution has been identified as one of several factors preventing these standards being met. Contributors to FIO pollution include domestic sources, agricultural pollution and wildlife (including birds). Increased investment for sewage treatment improvement is underway to help, in part, rectify this problem. In the pilot areas however, improved sewage treatment is not considered sufficient to reduce the probability of failure. The Scottish Executive has identified the need to implement measures that can help minimise FIO loads from agricultural activities to the watercourses in these areas.
1.4 Previous Work
The Scottish Executive is committed to achieving the Bathing Water Directive’s standards at all 60 identified bathing waters and so is piloting a range of innovative measures to tackle diffuse pollution in “at risk” bathing waters. In addition to this project there are a number of other initiatives, which are addressing linked pathways
for FIO pollution of the bathing waters. For instance:
• There is an extensive body of work, including complementary research on the Sandyhills catchment by the Centre for Research in Environment and Health (CREH), also commissioned by the Scottish Executive;
• Scottish Environment Protection Agency (SEPA) is supporting the Scottish Executive’s goal and its own commitment to good agricultural environmental practice with regard to controlling diffuse pollution. The Scottish Executive SEPA signage project is a public information source based on prediction of water quality and is active in the pilot catchments. The current project has adopted some of the parameters used in the signage project;
• SAC conducted research that resulted in the installation of fencing along catchment watercourse to prevent livestock access to water and a series of
other measures to improve farm infrastructure in the project “Research and Design of Pilot Schemes to Minimise Livestock Pollution to the Water Environment in Scotland”; (Scottish Executive, 2005) and,
• Previous anaerobic digestion work was carried out by the Scottish Executive in association with Scottish Water at Cumnock where cattle slurry was mixed with sewage sludge and treated within a combined treatment facility giving biogas, treated bio solids and a treated effluent liquor using operational infrastructure. Results showed that the average FIO log reduction from the cattle slurry feedstock in relation to the digested biosolids was approximately
2.39 log 10 reduction.
The outcome of the combined environmental and pilot plant research informs the economic and sustainability analyses. This analysis will advise the Executive on scheme value, effectiveness in achieving the objective, and the feasibility and need for a grant scheme if these technologies are to be funded beyond the pilot scheme.
1.6 Project Methodologies Capital works methodology The installation and commissioning of the AD plants and composting facilities is described in Chapter 2. The following process was used to provide operational AD plants and compost facilities for initial and medium term research into the effectiveness of on farm treatment of slurry and farmyard manure in protecting
designated bathing waters:
• Initial identification of 12 candidate farms within the two catchments was made by the Scottish Executive;
• The consortium undertook initial farm surveys (of the candidate farms) to identify suitable sites for either AD plants or composting facilities and hold discussions with the farmer to assess their interest in participating in the pilot project;
• Having identified suitable sites, formal agreements were entered into between the farmer and the Scottish Executive;
• Design of the AD and AC plants was undertaken;
• Following planning and building warrant acceptance, the HSE were informed of the construction works under the requirements of the C(DM) Regulations;
• Procurement of plant and construction contracts were implemented and construction was carried out;
• On completion of the plants, building control and SEPA inspections were undertaken, as appropriate;
• The AD plants and compost facilities were then commissioned and the farmers trained in their use and operation; and,
• As-built drawings, operation and maintenance manuals and a copy of the PEPFAA code were issued to each farmer.
Monitoring and Modelling Methodology The catchment assessment, monitoring protocols and results are discussed in Chapters 3 and 4. Development and application of the modelling is discussed in Chapter 5. These chapters describe;
• Development of a conceptual structure of farm systems and routes by which FIO may be lost from these to surface waters, through review of scientific literature, review of previous Scottish Executive reports and consultation with the Scottish Executive, SEPA and researchers from CREH;
• Development of monitoring plans and protocols, for the collection of environmental samples (soils; fresh, stored and treated manures) and FIO analysis (total coliforms, faecal streptococci and enterococci) and nutrient analysis (total and available N, P and K) by accredited laboratories and
collation and interpretation of data for:
• Using the Enviros modelling system AMBER, the conceptual model developed was encoded into a software tool, the Agricultural Risk Assessment Model (ARAM). This decision support system went through a number of iterations to meet the needs of the project. During this period
the following were undertaken:
• Development of a protocol for the use of ARAM, as agreed with the project steering committee;
• ARAM was then run to assess the FIO flux to surface waters (taken as a direct analogue to bathing water quality) for AD and composting treatment
and zero grazing options under rainfall event and non-rainfall event conditions. The contribution by a range of pathways has been assessed, the increase in flux due to landspreading of manures determined, and the ability to minimise this via manure treatment quantified; and,
• The risk reduction factors derived from the ARAM assessment have been applied to historic bathing water data to assess the potential improvements achievable through AD and composting treatment. The findings were fed into the sustainability appraisal.
Research Appraisal Methodology Building on the two previous strands of plant construction and commissioning and monitoring and modelling, the research protocol that is described in Chapters 6 to 8
• A review of the legislation relevant to AD plants and compost facilities on a farm scale and community scale basis;
• A sustainability appraisal set against the Scottish Executives’ strategic and policy priorities.
The research appraisal covered:
• A review of the climate change (including greenhouse gases), ammonia emissions including the minimisation of air pollutants emission and renewable energy aspects of the project; and potential odour issues
• Review of the volumes of material stored and handled;
• Whether a grant scheme would be required to facilitate such manure treatment to make an AD or composting approach viable and/or to fund such measures beyond the pilot project; and,
• Recommendations for further study.
The formal agreements with farmers expire on March 31 st 2009. Until such time the ownership of the plant is held by SEERAD. Access is also granted to relevant contractors for plant installation, surveying, monitoring, and maintenance activities during this period. The farmer is responsible for routine maintenance of the plant and this is detailed in the operation and maintenance manual.
2. DESIGN AND OPERATION During the project 10 plants were installed; 7 AD plants and 3 compost facilities on a total of 9 farms, with one farm having both an AD plant and a composting facility. These processes are described below. It is important to note that the project philosophy was to ensure that the design of the plants was robust and that the systems could cope with unforeseen eventualities that may arise, e.g. severe weather conditions affecting the process performance and leading to potential environmental harm. Also, as farmers were initially unfamiliar with the technologies and as operational consistency was essential for research results, the plants were designed to a standard that offered durability and reliability.
2.1 Initial Farm Surveys