Digestate back to land16th May 2013

Anna Becvar, Director

Earthcare Technical Ltd

What is Anaerobic Digestion (AD)?•A controlled microbial process where organic materials are broken down into simpler organic compounds in the absence of oxygen

• End products:

– Biogas (valuable energy source)

• ~ 60% methane, 40% carbon dioxide

– Semi-liquid organic fertiliser known as anaerobic digestate or ‘biofertiliser’

Digestate availability

• 2009, 17 UK AD plants.

• 2013, 109 + operational

• 10 BSI PAS 110 accredited Biofertiliser Certification scheme members

• The majority of digestate is spread on agricultural land at present

NNFC AD Plant Map: 8th May 2013

Types of digestate

Current options:

Whole digestate

Separated liquid

Separated fibre

‘Typical’ nutrient content food digestate (kg/tonne fresh weight)

Whole digestate

Major Nutrients Total Readily available

Potential value £/t

Nitrogen (N kg/t) 5.0 4.0 (80%) £3.48

Phosphate (P2O5 kg/t) 0.5 0.25 (50%) £0.18

Potash (K2O kg/t) 2.0 1.6 (80%) £0.80

aAssuming N = 87p/kg, P2O5 = 71p/kg, K2O = 50p/kg

Worth £4.50/tonne30m3/ha application = £135/ha

Readily available N (RAN) content of food-based Digestate based on 250 kg N/ha

Organic N

Readily available N

20%

Food based digestate

80% 30%70%

Pig slurry

Green compost

High readily available N >30% total N (NVZs)

<3%

Need to calculate the crop available Nitrogen

• Readily Available N (i.e. Ammonium-N by analysis) is potentially available for rapid crop uptake

• Organic N is broken down slowly to become available over months or years

• Crop Available N is the readily available N left for crop uptake after losses are taken into account

Organic materials – N supply and losses

To water (NH4-N, P, FIOs etc).

Nitrogengas

Volatilisation

Nitrification

SoilOrganic N

Immobilisation

Nitrous oxidegas

Ammonia gas

OrganicN

N

Ammonium

Denitrification

Nitrate

Crop available N Plant uptake

Calculate the Crop Available Nitrogen

1. Location – Rainfall and soil type

2. Timing of application (spring or autumn)

3. Method of application (e.g. surface, dribble bar, injection)

4. Use MANNER NPK to calculate crop available nitrogen

• Should use a FACTS Qualified Advisor

Also need to comply with:

• The CoGAP in England and Wales, PEPFAA in Scotland

•NVZ rules where applicable

Digestate

www.planet4farmers.co.uk/manner

Trailing hose 30%

Trailing shoe40%

Injection -

open slot70%

‘New’ application techniques

Ammonia (odour) emissions, crop contamination

N efficiency, spreading days and accuracy

Digestate – NVZs

• Liquid and whole digestate are classed as ‘high readily available N manures’ (i.e. > 30% of the total N present as readily available N) and therefore subject to application closed periods.

• High RAN digestate cannot be applied prior to legumes

• If fibre digestate analysis shows < 30% available N it will not be subject to application closed periods in a NVZ

• N Max:- from Jan 2014 these changes occur

• Total N in all organic manures applied will be counted.

• Most veg crops will have N max values applied. They were exempt before.

• Livestock manure fraction (%) counts towards Whole Farm Limit (170 kg N/ha)

Rules & Regulations on use

Digestate

BSI PAS110‘Waste’ digestate

Standard Permit SR2010No.4 Deployment (England & Wales)

PAS110 in Scotland (SEPA guidance)

PAS110 + ADQP in England & Wales a product

Paragraph 7 Exemption in Scotland

Crop & livestock manure digestate under farm control

Apply as for farm manures/slurries

In England and Wales waste digestate

• SR2010No4 Mobile Plant land spreading permit (£700 one off EA cost)

• Deployment per 50 ha block of land £760 EA cost

• What you need:– Spread risk maps of fields

– Up to date soil analysis

– Previous and future cropping

– Soil type

– Up to date digestate analysis (<12 months old)

• 25 working days for the deployment to be assessed

Quality Digestate (biofertiliser)

BSI PAS110 Input materials

• Input materials: Source segregated biowastes and/or biodegradable materials

• Shall not include contaminated wastes, products or materials

• No sewage sludge or its derivatives

• In England and Wales if following ADQP type of waste must be in the acceptable list

• In Scotland no ADQP but refer to the SEPA Position statement on classification of outputs

BSI PAS110 limits

Pathogens:

E Coli 1000 CFU/g

Salmonella spp Absent in 25g fresh matter

Potentially toxic elements (mg/kg dry matter)

Cadmium 1.5 Lead 200

Chromium 100 Mercury 1.0

Copper 200 Nickel 50

Zinc 400

Physical contaminants

Total glass, metal, plastic and any other non-stone >2mm

0.5% m/m dry matter

Stones >5 mm 8% m/m dry matter

Microbial pathogensE.Coli; colony forming units (CFU)/g fresh weight

0

40000

80000

120000

Food-based

digestate

Pig slurry Cattle slurry

CFU

(g/

fw)

<10

Source: Taylor et al. (2010); Defra “FIO-FARM” project

[ABPR/PAS 110 upper limit: 1000 CFU/g fresh weight]

Good Agricultural Practice when using digestate

• Storage – Covered stores (required for BSI PAS 110) reduce odour and ammonia loss

• Phosphate- Also a major consideration

• Timing - High readily available N means both whole and liquid digestates can only be applied outside application closed periods in NVZs and all digestates should only be applied when there is crop demand

• Method – Injection or trailing shoe/hose application equipment will both help minimise odours and conserve N

• Spread Risks - Follow a farm Manure Management Plan

• Work with neighbours - Tell them what you are doing and spread digestate with an awareness of their concerns/needs

Defra/WRAP/Zero Waste ScotlandDigestate and Compost in Agriculture

project, 2010-2014

Objectives

• ‘To quantify the effects of contrasting digestate and compost applications on soil and crop quality, crop available nitrogen supply and emissions to the air and water environments’

Field Experiments 2010-2014

WP1 Quantifying effects of contrasting digestate and compost applications on soil and crop quality

WP2.1 Looking at crop available nitrogen supply

WP2.2 GHG Hubs - effects of digestate and compost additions (compared to slurry and FYM) on ammonia (NH3) and Nitrous oxide (N2O) emissions, and at Wensum site, leaching losses: nitrate (NO3), soluble P and microbial pathogens

Follow the Digestate and Compost in Agriculture project, and download bulletins: www.wrap.org.uk/dc-agri

Thank you!

anna@earthcaretechnical.co.uk

www.earthcaretechnical.co.uk