Digestate Fertilizer: What It Is and How to Use It in Agriculture

Digestate fertilizer is one of the two principal outputs from an anaerobic digestion plant. Biogas receives most of the attention because it produces renewable energy, but the material remaining after digestion contains valuable nitrogen, phosphate, potash, sulphur and organic matter.

Used correctly, digestate can replace part of a farm’s purchased fertilizer requirement and return nutrients to the soil. Used carelessly, it can waste ammonia, create odour, damage water quality and apply more nutrients than the crop can use.

The right question is therefore not simply, “Can digestate be spread on farmland?” It is:

What nutrients are in this digestate, what does this crop require, and when and how should the material be applied?

This guide explains what digestate is, how its different fractions behave and the practical steps needed to use it as an agricultural fertilizer in the UK.

Originally published in May 2022. Completely revised and updated in September 2026 to reflect current nutrient-management guidance and the new Anaerobic Digestate Resource Framework for England.

What Is Digestate?

Digestate is the material remaining after biodegradable feedstocks have been broken down by microorganisms in an anaerobic digester.

The digestion process converts part of the organic matter into biogas, principally methane and carbon dioxide. It does not remove most of the mineral nutrients originally present in the feedstock. Much of the nitrogen, phosphorus, potassium and sulphur therefore remains in the digestate.

Anaerobic digestion also converts some organically bound nitrogen into ammonium nitrogen. This makes a proportion of the nitrogen more immediately available to plants than it was in the original feedstock.

However, digestate is not a uniform product. Its characteristics depend on:

• the feedstocks accepted by the AD plant;
• the proportions in which those feedstocks are blended;
• the digestion process and retention time;
• whether water or liquid recirculation is used;
• whether the digestate is separated after digestion;
• subsequent storage and treatment; and
• the presence of physical or chemical contaminants.

For that reason, a standard nutrient value should never take the place of a recent and representative analysis where an accurate fertilizer plan is required.

Is Digestate a Fertilizer, a Soil Improver or a Waste?

Digestate may perform more than one agricultural function.

Its readily available nitrogen, phosphate and potash give it fertilizer value. Its remaining organic matter can also contribute to soil organic matter and improve aspects of soil condition, particularly when a fibre-rich solid fraction is used.

Its legal status is a separate question.

Depending on how it was produced and the regulatory requirements it meets, digestate may be:

• a certified product that has achieved end-of-waste status;
• an agricultural material that was never classified as waste; or
• a waste that remains subject to waste-management controls.

Farmers should establish the material’s status before accepting it. Calling digestate a “biofertilizer” does not, by itself, remove waste controls.

Watch our digestate video below, but don't forget to continue reading here afterwards!

Whole, Liquid and Solid Digestate

Digestate is commonly supplied in one of three forms.

Whole digestate

Whole digestate is the material discharged from the digestion process before mechanical separation. It is generally pumpable and contains both liquid and fibrous components.

It can supply readily available nitrogen and potash while also returning some organic matter to the land. Its dry-matter content and nutrient concentration vary between plants.

Separated liquid digestate

A screw press, centrifuge or other separator can divide whole digestate into liquid and solid fractions.

The liquid fraction usually retains much of the ammonium nitrogen and potassium. It can therefore behave as a relatively fast-acting nitrogen and potash fertilizer. It can often be applied through trailing-hose, trailing-shoe or injection equipment.

Because much of its nitrogen is in an ammonium form, exposed surface application can result in significant ammonia loss. Application method, weather conditions and timing are important.

Separated fibre digestate

The solid or fibre fraction contains more dry matter and usually retains a greater proportion of the phosphorus and relatively stable organic material.

It is easier to stack and transport than whole digestate, although its suitability for storage and use still depends on its physical properties and regulatory status.

Fibre digestate may be used as a fertilizer and soil improver. In some circumstances it can be composted or processed further, but it should not automatically be described as compost. Compost and digestate are produced by different biological processes and are covered by different quality specifications.

What Nutrients Does Digestate Contain?

Digestate commonly supplies:

• nitrogen, including readily available ammonium nitrogen;
• phosphate;
• potash;
• sulphur;
• magnesium and other secondary nutrients; and
• organic matter.

The balance depends heavily on the feedstock and whether the material has been separated.

Food-based digestate can differ from farm-based digestate produced from slurry, manure and crops. A liquid fraction will differ from separated fibre produced at the same plant. Even successive batches from one plant may vary if its feedstock mixture changes.

The most useful information for a fertilizer plan normally includes:

• dry matter;
• total nitrogen;
• ammonium nitrogen;
• total phosphate;
• total potash;
• sulphur;
• magnesium; and
• potentially toxic elements or other parameters where relevant.

Ask the supplier for current analytical results and enough information to understand how representative they are. If a large quantity is being accepted or the analysis is uncertain, representative sampling and independent laboratory testing may be justified.

How to Use Digestate Fertilizer in Agriculture

A responsible application programme can be reduced to eight practical steps.

1. Confirm the digestate’s source and legal status

Find out what feedstocks were used and whether the digestate is certified, has achieved end-of-waste status or remains regulated as waste.

Request the relevant supply documentation, analysis and certification information. Do not assume that all digestate from an apparently similar AD plant has the same status.

2. Identify the form of digestate

Establish whether the material is whole digestate, separated liquor or fibre. This affects storage, transport, spreading equipment, nutrient availability and likely ammonia losses.

3. Test the soil and assess the crop requirement

Digestate should be applied to satisfy a genuine soil or crop need—not simply because storage is full.

Use current soil information and assess the nutrient requirements of the intended crop. In England, the Farming Rules for Water require nutrient applications to be planned so that they do not exceed soil and crop needs. Soil tests used for cultivated agricultural land must include the prescribed parameters and be no more than five years old.

4. Credit all nutrients supplied

Account for the crop-available nitrogen, phosphate, potash and other useful nutrients supplied by the digestate. Then reduce any subsequent manufactured-fertilizer application accordingly.

Failing to credit digestate nutrients can result in unnecessary fertilizer expenditure, nutrient surpluses and a greater risk of nitrate leaching, phosphorus loss, ammonia emissions and nitrous-oxide emissions.

5. Calculate a field-specific application rate

There is no single correct digestate application rate for every farm.

The appropriate rate depends on:

• the digestate analysis;
• crop type and expected yield;
• soil nutrient indices;
• soil nitrogen supply;
• previous crop and manure applications;
• time of year;
• soil type and drainage;
• application method;
• likely nutrient losses; and
• any regulatory limits or closed periods.

The calculation should be made using recognised nutrient-management guidance. The AHDB Nutrient Management Guide (RB209), Section 2 contains current information on organic materials, including digestate.

The 2026 edition includes updated information on crop-available nutrients and new tables for nitrogen availability following applications of food-based and farm-based digestate.

6. Choose the best application time

The greatest fertilizer benefit is normally obtained when digestate is applied shortly before or during a period of active crop nutrient demand, subject to soil and weather conditions.

Applying large quantities when crop uptake is low increases the risk of nutrient loss. Autumn application can be particularly inefficient for some crops and soils because nitrate may be exposed to leaching over winter.

AHDB illustrates how strongly timing can affect nitrogen value. Its guidance has shown that crop-available nitrogen from a spring application of whole digestate or separated liquor can be much greater than from an autumn application to cereals. The applicable value should be taken from the current RB209 tables for the particular material, crop, soil, timing and spreading method.

Do not spread digestate merely to create room in a store. Adequate storage is needed so that agricultural application can wait until there is a genuine crop requirement and acceptable field conditions.

7. Use suitable low-emission spreading equipment

Broadcast splash-plate spreading exposes a large surface area of liquid to the air. This can increase odour and the loss of valuable ammonium nitrogen as ammonia.

More controlled methods include:

• trailing-hose application;
• trailing-shoe application;
• shallow injection; and
• deeper injection where appropriate for the soil and crop.

A trailing hose places digestate in bands close to the ground. A trailing shoe parts the crop canopy and places the material at soil level. Injection puts the digestate into the soil, although it requires more power and is not suitable in every situation.

Where digestate is surface-applied to bare or cultivated land, prompt incorporation can conserve more nitrogen and reduce odour, provided incorporation is agronomically and legally appropriate.

8. Calibrate, monitor and record

Spreading equipment should be maintained and calibrated so that the planned rate is actually delivered. Uneven or inaccurate spreading can produce both under-fertilized and over-fertilized areas within the same field.

Records should include:

• the field and crop;
• date and time of application;
• digestate type and source;
• analysis used;
• quantity and application rate;
• application method;
• soil and weather conditions; and
• the nutrient contribution credited in the fertilizer plan.

How Much Digestate Should Be Applied Per Hectare?

Published examples often quote application rates in cubic metres or tonnes per hectare. Such figures can be useful for illustrating the calculation, but they should not be copied onto another farm without checking the analysis and crop requirement.

For example, two loads of digestate applied at the same volumetric rate could supply different quantities of readily available nitrogen if they came from different plants or different separated fractions.

The safe procedure is:

1. obtain a representative nutrient analysis;
2. calculate the nutrients supplied by each cubic metre or tonne;
3. estimate crop availability using current guidance;
4. compare the result with soil and crop need;
5. check all regulatory limits; and
6. set and calibrate the spreader to deliver the calculated rate.

A FACTS-qualified adviser can help where the nutrient calculation, field conditions or regulatory position is uncertain.

Which Crops Can Receive Digestate?

Digestate can potentially be used on grassland and many arable and energy crops. Whether it is suitable for a particular field depends on crop need, soil conditions, food-safety requirements, assurance schemes, contractual restrictions and the digestate’s source and quality.

Potential uses include applications to:

• grass and silage crops;
• cereals;
• oilseed rape;
• maize;
• sugar beet;
• some vegetable crops; and
• land being prepared for a following crop.

Extra care may be needed where crops are eaten raw, where the edible portion could come into contact with the material or where a crop-assurance protocol imposes restrictions.

Check the current rules and the requirements of the intended customer or assurance scheme rather than assuming that agricultural land application makes every crop acceptable.

Can Digestate Improve Soil?

Digestate can return organic matter to the soil, but its soil-conditioning effect varies.

Anaerobic digestion breaks down part of the readily degradable organic material. Digestate therefore does not have exactly the same organic-matter characteristics as the original manure or crop feedstock.

Separated fibre generally contributes more dry matter per tonne than a dilute liquid fraction. Repeated, properly managed applications may help maintain soil organic matter, but claims that digestate will automatically transform soil structure should be treated cautiously.

Its principal short-term value is often its nutrient content. The longer-term soil benefit depends on the fraction applied, application history, soil type and wider soil-management system.

Digestate Storage and Seasonality

An AD plant produces digestate throughout the year, while farmland can use it effectively only during suitable application windows.

This mismatch makes storage a fundamental part of digestate management.

Storage capacity should allow for:

• periods of low or no crop demand;
• closed spreading periods where applicable;
• waterlogged, frozen, snow-covered or flooded ground;
• wet weather and inaccessible fields;
• equipment breakdown;
• changes in cropping plans; and
• temporary loss of an outlet.

Stores should be designed and managed to prevent leakage, overtopping and water ingress. Covering liquid digestate storage can also reduce ammonia emissions and unnecessary dilution by rainfall.

Digestate storage and application cannot sensibly be planned after the AD plant is built. For the project-level implications, see our separate article: Digestate Management Planning: Start With the Outlet.

Why Does Digestate Smell?

Digestate is normally less odorous than the untreated feedstock because anaerobic digestion breaks down many readily degradable organic compounds. It is not, however, odour-free.

Odour can be influenced by:

• feedstock composition;
• digester stability and retention time;
• residual volatile compounds;
• storage conditions;
• hydrogen sulphide and other sulphur compounds;
• transport and agitation; and
• spreading method and weather.

A particularly strong or unusual odour may indicate poor feedstock quality, insufficient digestion, biological instability or a storage problem. It should not automatically be dismissed as an unavoidable characteristic of digestate.

Low-level placement, injection where suitable, prompt incorporation on cultivated land and avoiding unsuitable weather conditions can reduce odour during application.

Reducing Ammonia Losses from Digestate

The readily available nitrogen that makes digestate valuable also makes it vulnerable to ammonia loss.

Losses are generally increased by exposed surface application, warm and windy conditions, high-pH material and a long delay before incorporation.

Practical controls include:

• using covered storage;
• avoiding unnecessary agitation;
• applying during cool, calm conditions where practicable;
• using trailing-hose, trailing-shoe or injection equipment;
• placing liquid below the crop canopy; and
• incorporating surface-applied material promptly on bare soil.

Reducing ammonia loss retains more fertilizer nitrogen for the crop. It is therefore both an environmental measure and a way of protecting the economic value of the digestate.

PAS 110 and the Biofertiliser Certification Scheme

BSI PAS 110 is the UK specification for whole digestate, separated liquor and separated fibre derived from the anaerobic digestion of biodegradable materials.

The Biofertiliser Certification Scheme provides independent certification against PAS 110 and the applicable end-of-waste requirements.

Certification provides assurance about matters such as approved inputs, process control and digestate quality. It does not mean that the digestate can be spread at any rate, at any time or on any field.

The recipient remains responsible for applying it lawfully and in accordance with soil and crop requirements.

The 2025 Anaerobic Digestate Resource Framework for England

In October 2025, the Environment Agency published a new Anaerobic Digestate Resource Framework for England. It replaces older assumptions about how qualifying digestate from source-separated biodegradable waste achieves end-of-waste status.

Among other requirements, qualifying digestate must:

• be produced from permitted source-separated biodegradable materials;
• be processed in accordance with PAS 110;
• be independently certified through an approved certification body;
• meet the applicable quality and record-keeping requirements;
• need no further treatment before its intended use;
• have a certain and lawful use; and
• be supplied and used in accordance with an appropriate nutrient-management plan.

A particularly important point is that certified digestate is not automatically a non-waste product forever. Under the framework, it can become waste again if it is discarded, stored indefinitely with little prospect of use or applied in excess of soil and crop requirements.

This makes nutrient planning part of the material’s lawful use—not merely an optional exercise intended to improve fertilizer efficiency.

The framework applies to England. Farmers and operators in Wales, Scotland and Northern Ireland must consult the requirements of their respective environmental regulators.

Farming Rules for Water in England

The Farming Rules for Water treat anaerobic digestate as an organic manure.

Before applying it in England, the land manager must plan the application, check that it does not exceed soil and crop requirements and assess pollution risks, including weather and field conditions.

Organic manure must not be applied:

• to waterlogged, flooded or snow-covered soil;
• when the soil has been frozen for more than 12 hours in the preceding 24 hours;
• within 50 metres of a spring, well or borehole;
• within 10 metres of inland freshwaters or coastal waters, except where a stated exception applies; or
• where other factors create a significant risk of pollution.

Approved precision equipment can reduce the normal watercourse buffer to six metres in qualifying circumstances. The current government guidance should be checked before relying on any exception.

Land in a Nitrate Vulnerable Zone is subject to additional controls, including limits, record-keeping requirements and closed periods. Different but related rules operate in Wales, Scotland and Northern Ireland.

Benefits of Digestate Fertilizer

When properly managed, digestate can:

• replace part of the farm’s manufactured nitrogen, phosphate and potash requirement;
• reduce expenditure on purchased fertilizer;
• return nutrients from food waste, manure and other biomass to productive land;
• supply readily available nitrogen to growing crops;
• contribute organic matter, particularly through separated fibre;
• support a more circular nutrient economy; and
• provide a planned and beneficial outlet for an AD plant’s principal material output.

Limitations and Risks

Digestate also presents limitations that should not be concealed.

• It is bulky and expensive to transport when dilute.
• Nutrient composition can vary.
• Storage is needed between suitable spreading periods.
• Ammonia can be lost during storage and application.
• Excess nitrogen and phosphorus can pollute water.
• Odour can cause complaints.
• Physical contaminants can restrict acceptability.
• Some digestates remain wastes and require regulatory controls.
• Farm location and local nutrient demand may not match the volume produced.

Digestate is therefore not “free fertilizer”. Even where the material itself has a low or negative purchase price, analysis, storage, transport, spreading, record keeping and regulatory compliance all have costs.

Digestate Fertilizer Price and Value

There is no reliable national price for digestate fertilizer.

Its value depends on:

• nutrient analysis;
• current manufactured-fertilizer prices;
• distance from the AD plant;
• haulage and spreading costs;
• dry-matter content;
• whether storage is available;
• seasonal demand;
• certification and quality; and
• the local balance between digestate supply and available land.

In some locations, farmers may pay for a nutrient-rich product. Elsewhere, an operator may supply it at low cost or contribute to transport and spreading because securing a reliable outlet has value to the AD plant.

A sensible valuation calculates the replacement value of crop-available nutrients and then deducts the costs of storage, transport, application and any additional management burden.

Frequently Asked Questions

Is digestate a fertilizer?

Yes. Digestate contains nitrogen, phosphate, potash and other plant nutrients and can replace some manufactured fertilizer. Its legal classification may still be either a product or a waste, depending on its source and compliance status.

Is digestate the same as slurry?

No. The two may look similar and can use similar handling equipment, but digestate has passed through anaerobic digestion. This changes its organic matter and converts some organic nitrogen into more readily available ammonium nitrogen.

Is digestate the same as compost?

No. Digestate is produced without oxygen in an anaerobic digester. Compost is produced by an aerobic process. Separated digestate fibre may subsequently be composted, but it should not be called compost merely because it looks fibrous.

Can digestate replace all manufactured fertilizer?

Sometimes it can meet a large proportion of a crop’s requirement for particular nutrients, but it rarely matches every nutrient requirement perfectly. A nutrient plan should identify what the digestate supplies and whether a supplementary fertilizer is needed.

Can digestate burn or damage plants?

Excessive or poorly placed digestate can damage crops, especially because of ammonium, salts or inappropriate application conditions. It should be analysed, diluted only where appropriate and applied at a rate and by a method suitable for the crop.

Can digestate be used directly on garden plants?

Commercial farm digestate should not be treated like a ready-to-use bottled garden feed. Its strength, hygiene, contaminant content and legal status must be known. Gardeners should use a product specifically supplied and labelled for horticultural or domestic use and follow the supplier’s directions.

Why does digestate smell?

It retains volatile compounds and nutrients from the original feedstock. Poor digestion, storage conditions and surface spreading can increase odour. Low-emission spreading and prompt incorporation can reduce it.

Does PAS 110 mean digestate can be spread anywhere?

No. PAS 110 certification addresses production and quality requirements. The user must still comply with nutrient, water-protection, land-use and other applicable rules.

What is the best time to spread digestate?

The best time is generally when a growing crop can use the nutrients and soil and weather conditions permit safe application. The answer varies with crop, soil, digestate type and location. Current RB209 guidance and all applicable regulations should be used.

What else can be made from digestate?

Depending on its properties and the processing used, digestate may have outlets beyond direct agricultural spreading. These can include composted products, growing-media ingredients, recovered nutrient products and other specialist uses. See 16 Uses for Biogas Digestate for a broader discussion.

Conclusion: Treat Digestate as a Nutrient Resource

Digestate can be a valuable fertilizer, but its value is realised only when it is treated as an analysed nutrient resource rather than an unwanted residue from biogas production.

Good practice begins by confirming the material’s quality and legal status. It continues through soil testing, crop planning, representative analysis, suitable storage and accurate low-emission application. The nutrients supplied must then be fully credited when planning any additional fertilizer.

That approach saves purchased fertilizer, reduces avoidable emissions and protects soil and water. It also gives the AD plant something every successful facility needs: a lawful and dependable outlet for the digestate it produces every day.

This article provides general information and is not a substitute for site-specific agronomic or regulatory advice. Requirements vary across the UK and may change. Consult the relevant regulator and a suitably qualified agricultural adviser before accepting or applying digestate.

[Published May 2022. Rewritten September 2026.]