Farmers often spend too much on chemical fertilisers (also known as mineral fertilizers because they are mined from geological deposits). These can harm the soil and the environment. Finding a better way to grow crops is a big challenge.
Digestate fertiliser from anaerobic digestion is a strong solution. It uses organic waste to make nutrients so the result is a renewable fertilizer. Up to 95% of the input turns into digestate. All nitrogen, phosphorus, and potassium stay in the digestate.
This article shows how digestate fertiliser can cut costs and boost your crops. Learn how to use it today.
What You Will Learn from this Article
- Cost-Effective Alternative: Digestate fertiliser retains up to 95% of input nutrients like nitrogen, phosphorus, and potassium, reducing farmers' reliance on expensive chemical fertilisers.
- Sustainable Production: Produced through anaerobic digestion, digestate transforms organic waste into valuable biogas and nutrient-rich fertiliser, supporting a circular economy.
- Nutrient-Rich Soil Amendment: Contains 2.3–4.2 kg nitrogen, 0.2–1.5 kg phosphorus, and 1.3–5.2 kg potassium per tonne, enhancing soil fertility and promoting healthy crop growth.
- Regulatory Compliance: Must meet PAS110 standards in England and Wales or SEPA regulations in Scotland, ensuring high quality and safety for agricultural use.
- Environmental Benefits: Reduces carbon emissions and fossil fuel use, while effective waste management lowers the farming sector’s carbon footprint.
Understanding Anaerobic Digestion
Anaerobic digestion breaks down plant and animal waste without using oxygen. This process produces biogas for energy and digestate that fertilises crops, supporting sustainable farming.
The Process of Anaerobic Digestion
Organic material like animal manure and food waste enters the anaerobic digester. Inside, it breaks down without oxygen. Methanogenic archaea help convert the material during methanogenesis.
The process happens in stages. First, bacteria break down the material into simpler compounds. This produces biogas and digestate. The digestate makes up about 90-95% of what was fed into the digester.
Biogas can be used for energy, reducing reliance on fossil fuels.
Digestate is a rich soil conditioner. It improves soil fertility and structure. Farmers use it to enrich their crops. The process also helps manage waste effectively. By turning waste into valuable products, farmers support a circular economy.
Digestate replaces synthetic fertilisers, lowering fertiliser costs. This sustainable method reduces the carbon footprint of farming.
Anaerobic digestion transforms waste into valuable resources, promoting sustainability on the farm.
Biogas and Digestate Production
Anaerobic digestion breaks down organic matter without oxygen in biogas plants. Methanogen bacteria digest animal wastes, farmyard manures, and biowastes, producing biogas as a renewable energy source.
The process leaves behind digestate, which includes leftover indigestible material and dead microorganisms. All nitrogen, phosphorus, and potassium from the feedstock remain in the digestate, ensuring these essential nutrients are retained for soil health.
This nutrient-rich digestate serves as an effective soil amendment, enhancing soil conditioning and supporting sustainable farming practices.
Benefits and Uses of Digestate
Digestate enriches soil with essential nutrients, promoting healthy crop growth. Farmers use it as a natural fertiliser, supporting sustainable farming practices.
Nutrient Properties of Digestate
Digestate supplies essential nutrients for healthy crop growth. It contains 2.3–4.2 kg of nitrogen, 0.2–1.5 kg of phosphorus, and 1.3–5.2 kg of potassium per tonne. These nutrients improve soil fertility and support robust plant metabolism.
Compared to raw slurry, nutrients in digestate are more available to plants, enhancing crop production and soil health.
Digestate offers a balanced nutrient profile, making it an effective alternative to artificial fertilisers.
Agricultural Use and Guidelines for Digestate
Using digestate as a fertiliser supports sustainable farming. It enhances soil health and reduces reliance on synthetic products.
- Nutrient Properties: Digestate contains essential nutrients like phosphorous (P) and ammonium nitrate. These nutrients boost soil fertility and crop growth.
- Application Methods: Spread digestate evenly across fields using fertiliser spreaders. Ensure proper coverage to maximise nutrient uptake by plants.
- Quality Standards: Adhere to PAS110 standards in England and Wales. In Scotland, follow SEPA regulations to ensure digestate quality and safety.
- Guidelines Availability: Access detailed agricultural guidance on digestate from the WRAP website. The Digestate & Compost in Agriculture Project offers additional resources.
- Managing Nutrients: Use fixed nutrient ratios to prevent imbalances. Monitor soil nutrient levels regularly for optimal plant health.
- Use Cases: Apply digestate to various crops, including maize and sugarcane. It also benefits soil remediation and supports commercial farming practices.
- Environmental Benefits: Reducing synthetic fertiliser use lowers fossil fuel consumption. This practice contributes to waste management and the bioeconomy.
- Limitations: Be cautious of ammonia volatilisation when applying digestate. Adjust application rates in nitrate vulnerable zones to protect water quality.
Standards for Digestate Quality
To ensure high-quality digestate, adherence to industry standards is essential.
| Aspect | Details |
|---|---|
| Quality Protocol & PAS110 | Digestate must meet Quality Protocol and PAS110 standards in England and Wales to avoid waste classification. |
| Mandatory Compliance | Compliance with the Quality Protocol is optional. Without it, digestate requires waste management controls. |
| PAS110 Specifications | PAS110 sets industry standards for digestate from source-segregated biodegradable materials. |
| Bio-fertiliser Certification | AD plants meeting PAS110 can market their digestate as “Bio-fertiliser.” |
Regulatory Framework for Anaerobic Digestion Products
Regulatory standards ensure anaerobic digestion products are safe and effective for farming. In England and Wales, producers must follow the PAS110 protocol, while Scotland requires compliance with SEPA regulations and certification through the Biofertiliser Certification Scheme.
Quality Protocol and PAS110 Compliance in England and Wales
The Quality Protocol sets clear criteria for anaerobic digestate from biowaste. It ensures digestate from anaerobic digestion plants is safe for use on soils. Digestate must meet Quality Protocol and PAS110 standards to avoid being classified as waste.
PAS110 helps producers verify their digestate's consistent quality. Farmers rely on these standards for effective nutrient management and soil amendments.
Consistent quality in digestate production is essential for sustainable farming.
Compliance with Quality Protocol and PAS110 guarantees that digestate is nutritious and suitable for cultivation. Meeting these standards supports the use of animal slurries and agricultural wastes in agriculture.
Next, explore SEPA Regulations in Scotland.
SEPA Regulations in Scotland
SEPA’s Regulatory Position Statement must be followed in Scotland. Use PAS110 certified anaerobic digestates to meet SEPA guidelines. Uncertified anaerobic digestates do not count towards recycling targets under the Zero Waste Plan.
Farmers must ensure their digestate complies with SEPA standards to benefit from recycling incentives.
Certification through the Biofertiliser Certification Scheme
The Biofertiliser Certification Scheme (BSC) ensures that digestate used as biofertiliser meets safety and quality standards. Farmers and gardeners can trust certified digestate to provide essential nutrients for their crops.
Renewable Energy Assurance Ltd. manages the BSC across England, Scotland, Wales, and Northern Ireland. This certification process includes testing for nutrient properties and contaminants, ensuring the digestate is suitable for agricultural use.
By choosing BSC-certified biofertilisers, you support sustainable farming practices and enhance soil health effectively.
Practical Applications and Limitations of Digestate
Digestate can be applied by spreading or injecting it into the soil, but fixed nutrient ratios may restrict its use—learn how to make the most of it on your farm.
Methods to Apply Digestate
Applying digestate boosts soil health and crop yields. Farmers and gardeners have several effective methods to apply it.
• Tanker Application: Use tankers to spread digestate directly on fields. This method suits large areas and ensures even coverage.
• Umbilical Pipelines: Inject digestate through pipelines linked to anaerobic digesters. It allows continuous application, saving time and transport costs.
• Separation into Liquor and Fibres: Divide digestate into liquid and solid parts. Liquor can be used for irrigation or hydroponics. Fibres enhance soil structure and can be turned into composts.
• Spraying: Apply liquid digestate with sprayers. This technique provides precise nutrient distribution and reduces waste.
• Incorporation with Machinery: Combine digestate with ploughs or seed drills. Integrating nutrients into the soil helps plant roots absorb them efficiently.
Choosing the right method depends on your equipment and crop needs.
Use of Separated Liquor and Fibres
Separated liquor and fibres from anaerobic digestion offer valuable resources for farming. They enhance soil health and provide essential nutrients.
- Liquid Fraction Usage
- Contains less than 6% dry matter, making it easy to apply to crops.
- Suitable for irrigation systems or spraying, ensuring even nutrient distribution.
- Rich in organic compounds like acetate and formic acid, which promote plant growth.
- Can be used to fertilise a variety of energy crops and oilseed rape.
- Fibres Application
- Fresh fibres act as effective soil conditioners, improving soil structure and water retention.
- Enhance nutrient availability, supporting better plant nutrition and growth.
- Can be composted to create vermicompost, further stabilising nutrients for safe use.
- Ideal for use with dairy farms and poultry litter, recycling waste into valuable soil amendments.
- Separated Liquor and Fibre Benefits
- Reduces waste disposal needs, supporting waste-to-energy initiatives.
- Lowers reliance on chemical fertilisers, promoting sustainable farming practices.
- Supports biorefinery processes by integrating organic waste into farming systems.
- Enhances soil microbiome, boosting natural decomposition and nutrient cycling.
Next, explore the strategic considerations for applying digestate in farming operations.
Challenges with Fixed Nutrient Ratios in Digestate
Digestate has a fixed mix of nutrients, which can limit its use on different farms. Farmers need specific levels of nitrogen, phosphorus, and potassium for their crops. This rigidity means digestate may not always meet those needs.
For example, a gardener might require more potassium for fruit trees than what standard digestate offers.
WRAP has conducted studies on improving digestate through various treatment methods. Techniques like composting and nutrient separation can help adjust the nutrient balance. These processes allow farmers to tailor the digestate to better suit their soil and crop requirements.
Without such enhancements, the fixed nutrient ratios can restrict the effectiveness of digestate as a fertiliser. Understanding these challenges is crucial for optimising its use in sustainable farming.
Strategic Considerations for Applying Digestate
Evaluate your farm’s capacity to handle digestate applications effectively. Ensure compliance with local regulations to protect your environment and crops.
Assessing Land Availability
Assessing land availability is essential for effective digestate application. Ensure that suitable land is nearby to optimise usage.
- Calculate Land Requirements
Use the AD calculator to determine the exact land area needed based on your digestate production. - Choose Nearby Locations
Select land close to the anaerobic digester to reduce transportation costs and emissions. - Evaluate Soil Quality
Test the soil to ensure it can effectively absorb nutrients from the digestate. - Match Crops with Nutrients
Apply digestate to crops like maize and sugar plants that benefit from its nutrient properties. - Check Regulatory Compliance
Ensure the land is not in nitrate vulnerable zones and meets SEPA and PAS110 standards. - Plan Application Methods
Decide on spreading techniques such as injection or surface application based on land type. - Ensure Sufficient Space
Verify that there is enough land available near the digester for ongoing digestate use.
Managing Applications in Nitrate Vulnerable Zones (UK)
Managing fertiliser applications in Nitrate Vulnerable Zones (NVZs) requires careful planning. Adhering to regulations ensures environmental protection and compliance.
- Comply with NVZ Regulations: Familiarise yourself with local NVZ rules. In England, 62% of land is within NVZs, while 4% of Welsh land falls under the same zones.
- Test Digestate Quality: Ensure your digestate meets quality standards. Check nutrient levels and remove any contaminants. Utilise the Biofertiliser Certification Scheme for verification.
- Plan Application Timing: Apply digestate during suitable seasons. Avoid wet periods to reduce nitrate leaching. Schedule applications when crops can uptake nutrients effectively.
- Determine Correct Dosage: Calculate the nutrient needs of your crops accurately. Prevent over-application to minimise environmental impact. Use precise measurement tools for dosage.
- Use Appropriate Application Methods: Spread digestate evenly to prevent runoff. Consider incorporating it into the soil through tillage. Employ techniques that enhance nutrient retention.
- Monitor Nitrate Levels: Regularly test soil nitrate concentrations. Adjust application practices based on monitoring results. Maintain nitrate levels within safe limits to protect water quality.
- Maintain Application Records: Keep detailed records of all digestate applications. Include dates, locations, and amounts used. Ensure traceability and compliance with regulations.
- Assess Land Availability: Evaluate available land within NVZs for digestate application. Optimise land use to balance fertiliser needs and environmental protection.
Next, explore the restrictions on grazing after applying digestate.
Restrictions on Grazing Post-Digestate Application
After managing applications in nitrate vulnerable zones, it's crucial to understand grazing restrictions. These rules ensure farm safety and compliance with regulations.
- Digestate Source Requirement: If digestate is from anaerobic digestion plants treating animal by-products, a grazing ban is mandatory.
- Ban Duration: Livestock must not graze on treated land until the official ban period ends, as specified by regulations.
- Access Restrictions: Animals are strictly prohibited from accessing areas where digestate has been applied during the ban period.
- Regulatory Compliance: Adhere to SEPA regulations in Scotland and PAS110 standards in England and Wales to maintain quality and safety.
- Certification Needs: Ensure digestate is certified through the Biofertiliser Certification Scheme to meet all legal requirements.
- Health Safeguards: Prevent livestock exposure to treated land to avoid potential health risks from residual substances in the digestate.
Conclusion
Digestate fertiliser offers a sustainable alternative to chemical fertilisers. Farmers gain rich nutrients that boost plant growth. Using digestate reduces energy use and cuts carbon emissions.
With proper application, it enhances soil health effectively. Embracing digestate supports eco-friendly farming now and for the future.
FAQs
1. What is digestate fertiliser and how is it produced?
Digestate fertiliser is made from sewage sludge, kitchen waste, and other organic materials. Through anaerobic digestion, methanogens bacteria break down these materials without oxygen. This process produces biochars and nutrient-rich fertiliser for sustainable farming.
2. How does digestate fertiliser contribute to biogas production?
During anaerobic digestion, methanogens bacteria convert organic waste like sewage sludge and kitchen waste into biogas. This biogas can be used as biofuels. Digestate fertiliser remains after biogas production and enriches the soil, making the process sustainable.
3. Can digestate fertiliser help manage plastic waste?
Yes, digestate fertiliser can aid in managing plastic waste. Through processes like fermenting and pyrolysis, certain plastics can be broken down. This reduces plastic pollution and transforms waste into useful biofuels and fertilisers.
4. What role do biochars play in sustainable farming with digestate fertiliser?
Biochars are created during the anaerobic digestion of organic waste. When added to soil, biochars improve soil health, increase water retention, and enhance nutrient availability. This supports sustainable farming by boosting crop growth and reducing the need for chemical fertilisers.
5. How does using digestate fertiliser benefit the environment?
Using digestate fertiliser recycles waste from sugar industries, kitchen waste, and sewage sludge. It reduces greenhouse gas emissions by capturing biogas. Additionally, it enriches the soil with nutrients, promoting sustainable farming and decreasing reliance on synthetic fertilisers.
