adding value to digestate: landscaping, regeneration and horticultural sector … · 2019-03-22 ·...
TRANSCRIPT
Adding value to digestate: landscaping, regeneration and horticultural sector trials.
18th European Biosolids & Organic Resources Conference 19-20th Nov 2013
Jacks Guinness – WRAP Project Manager
What I’ll cover…
Background and context
Work to develop markets for digestate
Landscape & Regeneration
Horticulture
Conclusions
About WRAP
WRAP’s vision is a world without waste, where resources are used sustainably. We help businesses, individuals and communities reap the benefits of reducing waste, developing sustainable products and using resources in an efficient way.
Why is WRAP involved?
Policy drivers – AD Strategy and Action Plan
Closing the loop
Digestate – key for closing the nutrient recycling loop
Reduces use of primary resources/fertilisers - phosphate is a finite resource
Market model
Supply Demand Sustainable Market
Volume
Location
Product/Price
End user requirements
Supply Digestate volumes
2012 tonnage (actual)
2016 tonnage (predicted)
Waste fed AD sites 678, 465 1,891,825
Location 122 operational facilities (68 Waste fed, 54 Farm fed) Proximity to markets
Addressing the barriers
Developing the market for digestate by:
Building safe and secure markets
Promoting and developing BSI PAS110 specification
Building skills and knowledge – operators and end users
Obtaining evidence on digestate benefits – research and field trials
Investigating new markets and opportunities
Demand - what end-users want
Consistency
Low risk
Fitness for purpose
CONFIDENCE/ TRUST
AD risk assessment
Clostridium botulinum Herbicides in
digestate
Impact of pasteurisation on
pests and diseases
Compost/digestate data
Biofertiliser matrix
Odour/ammonium
Demonstrating digestate safety and fitness for purpose
Flavour/odour taints
Food Standards Agency/Crop Assurance schemes e.g. Red Tractor
Promoting and developing quality products – BSI PAS110
Transforming ‘waste’ digestates into ‘products’
12 operators certified to BSI PAS110
Certified tonnage = 437,900 tonnes pa (registered throughput)
Under review www.biofertiliser.org.uk
Why use digestate?
Nutrients N, P, K, S, Mg Trace elements
Organic matter (fibre)
Can save money
Reduce carbon footprint
At present almost all digestate is used in agriculture - experiments under DC-Agri
Most UK digestates are low dry matter (<10%)
Can be separated
– Fibre
– Liquor
Different fractions have different nutrient profiles
– Different potential uses
– Different potential markets
Developing digestates
Other potential markets
Brownfield site restoration – soil improvement (growing energy crops)
Soil manufacture
Turf establishment
Sports and amenity turf maintenance
Horticultural applications
Establishing energy crops on brownfield land
– Fibre/whole digestates (compost)
Fertilising energy crops on brownfield land
– Whole and liquor digestates
Fertiliser for turf growing and maintenance uses
– Liquor digestates
Informing future reviews of allowable markets within ADQP
All projects will have an associated knowledge exchange programme
L & R Field experiments 2012 -2014
Using digestate as a biofertiliser for established short rotation coppice (SRC) willow
Burntstump - restored landfill site in
Nottinghamshire growing SRC willow for the last two years
Trial investigates the use of digestate as a biofertiliser to improve crop yields using specialised irrigation equipment within the plantation
Trial will investigate effects on:
SRC willow yields
Soil physical, chemical and biological properties
Using digestate as a sport and amenity turf fertiliser Examines the use of liquid fraction
digestate as a fertiliser for sports and amenity turfs
Replicated research trials at Cranfield University and the Sports Turf Research Institute
Investigating turf quality, soil health & practical application
Using digestate to establish perennial grasses for AD feedstock
2 sites: Landfill site (Essex) and Quarry (Leics)
Grasses grown on sub-soil bunds at the edge of operational areas
Compost applied to improve soils prior to planting
Whole digestate then applied and repeated at intervals
Potential benefits: low cost, diversification for operators
Findings to date
Fibre useful as a soil improver - limited quantities available
Early evidence of yield increases
Liquors good nutrient source but dilute and need ultra filtering to avoid blockages on standard spraying and spreading equipment
Digestate behaves like fertiliser but application rates need to be managed carefully to avoid problems e.g. scorching, high conductivity
Can be difficult to handle
Odour a barrier to use on sports and amenity turf
Horticulture feasibility trials
Exploring the potential for quality digestate:
As an addition to wood/bark chips to create viable growing media blends
As a liquid feed for containerised strawberry production
In soil-less hydroponic trials for tomatoes
Use of the fibre in container composts
Questions to answer:
– What are the constraints?
– Can these be overcome?
– Are there business benefits?
– Should the ADQP be changed?
Bark admixtures Formulation and testing of novel organic growing media using quality digestates for the production of containerised plants. Bark + other sustainable materials + digestates = novel growing media
Making the admixtures The main selection criteria were EC, structure
and consistency (not too wet or too dry)
Standard ingredients trialled
The final admixtures:
60% bark, 30% wood fibre, 10% top soil + digestate
Trial
Controls (industry standards)
Peat-based control (PC)
Peat-free control (bark & wood fibre based BC)
4 digestates – each with 5 admixtures
5 replicates = 110 plants per trial
Plants grown were cyclamen, fern and pine
Monitored regularly for growth & plant health
Results
Cyclamen
Large variability in plants
Flowers were produced in all treatments
Corms all healthy (except 1) and of similar weights
All plants grew and senesced at approx the same time
Ferns
Potential for liverwort control using admixtures
No significant differences for the number of fern fronds and frond length
No significant difference in the root:shoot ratio in any of the treatments
Highest % of digestate (1000ml in 5 lit of mix) showed reduced foliage quality & reduction in total plant weight
Pines No differences – foliage quality good for all treatments
And no significant differences in: Growth Quality Fresh weight Dry weight
Strawberry cultivation – liquid feed
Can quality digestate be used as a nutrient source for trickle irrigation in strawberries to replace conventional nutrient solutions used in commercial production?
Control (industry standard) and 6 digestates trialled, grow bags with trickle irrigation.
Assessed for foliage colour and quality, fruit quality and dry weight of plants
Nitrogen availability
The digestates contained 10 - 25 times too much mineral N; all in the form of ammonium
Digestates were diluted (up to 51 times) to achieve 120mg/l total mineral nitrogen
Some nitrate is required so diluted digestates were amended to provide:
60% ammonium-N (from digestate)
40% nitrate-N (from amendment)
Establishment
Strawberries planted end of Jan 2013
Feeding started three weeks later
Digestate (day 18) Control
Total fruit yield at harvest
Average fruit weight at harvest
Conclusions
Diluted and amended digestates can successfully be used to produce a fertigated strawberry crop
Fruit yield and quality yield are (mostly) maintained (under experimental conditions)
Digestate based fertilisation has the potential to significantly reduce overall fertiliser cost.
The cost saving is 1% or less of the produce crop value
Potting compost blends – fibre & green waste compost
Key study questions:
• Will plants survive in composts free of peat and containing significant AD Fibre mixed with composted green waste?
• How will this range of compost blends perform in comparison to established retail formulations?
• How will these novel compost mixtures perform under near commercial growing environments and practices?
Findings
• Inclusion of a composting phase after mixing of digestate & GWC is necessary
• AD Fibre can be reliably incorporated as a growing media component up to at least 50% by volume
• AD fibre used in this study did not require pH adjustment or nutrient leaching prior to use in order to produce commercially satisfactory levels of growth in the majority of instances.
• The physical structure blends appeared stable over 3 months
• average bulk density values of the blends were higher than control composts but may lend water holding benefits for some needs
• Further work needed to assess optimum irrigation management
• Its potential may be as a bulk replacement or / and as a slow release fertilizer source
Aim: Determine feasibility of using liquid digestate as nutrient medium for hydroponic solution. Digestates used: 2 derived from food waste (FW1 and FW2) (PAS110) and 1 from cattle dung (CD). Crops grown: Tomato and lettuce – focus here is tomatoes. System used: Open system (does not recirculate). Potential problem: High ammonium concentration.
Tomatoes
Tomatoes – Set-up
Set-up: Series of closed trials using Moneymaker and Super Sweet 100. Whole digestates were diluted and replaced weekly. Solutions were topped up as required and tubs aerated.
Tomatoes – Digestate dilutions
FW1 FW2 CD
Total-N (mg/L) 4327 6912 3359
Ammonium (mg/L) 4227 6654 2846
Nitrate (mg/L) 100 258 513
Excess total-N (x) 38 (30)* 61 (48) 30 (23)
Ammonium (% of total) 98 92 85
Diln. needed (x) 374 (294) 589 (462) 252 (198)
Nitrate amendment required (mg/L) 101 (129) 102 (129) 100 (127)
N-required pre-flowering (mg/L) 113
N-required post-flowering (mg/L) 144
* Where there are two sets of numbers, those outside the brackets refer to pre-flowering solutions and those within brackets refer to post-flowering solutions.
Findings
average weight per tomato statistically the same across treatments. Total yield was the same across all treatments. No significant differences Differences in total number of tomatoes were. The standard solution (INO)
generally yielded more, but the same number as for FW1 (statistically). trend towards smaller tomatoes from plants grown in the standard
inorganic solution – may explain similarity in overall yield despite more tomatoes being produced by those plants
System is feasible & can offer some potential savings especially if nutrients are re-circulated and nitrification issue is cracked.
Overall Findings – Hort Trials
Currently not a permitted use – EA permit /exemption required
Recommend using PAS110 QP - compliant digestates
Growing media - fibre demonstrates good potential
Useful nutrients
Different kinds can be difficult to handle
Hydroponics – high N content
Needs substantial dilution to substitute for conventional fertigation solutions
But system feasible if nitrification cracked
Handling and odour issues may be present
Further work recommended
Recent publications
• ‘Digestate enhancement & treatment’ (Nov 2012) • Identification & review of technologies &
treatment for a wide range of digestates • ‘Market expectations and requirements
for digestate’ (March 2013) • End user product needs
Recent publications – contd.
• ‘Evidence for digestate use in different UK markets: an annotated bibliography’ (June 2013) • Published evidence on digestate
benefits
• ‘Digestate distribution models’ (Aug 2013)
• Looked at different organic recycling industry supply/distribution models to provide information to AD industry
Conclusions
Digestate can be a very valuable resource but has to be managed carefully
We’ve come along way but there is still more to do
Operators need to understand their products and potential markets
Proven enhancement technologies needed to develop products if new markets are to be viable
Further work needed to develop the case for digestate use in potential new markets
Thank you www.wrap.org.uk
www.wrap.org.uk/landscaping
www.wrap.org.uk/horticulture