Adding value to digestate: landscaping, regeneration and horticultural sector trials.

Transcription

1 Adding value to digestate: landscaping, regeneration and horticultural sector trials. 18 th European Biosolids & Organic Resources Conference 19-20th Nov 2013 Jacks Guinness WRAP Project Manager

2 What I ll cover Background and context Work to develop markets for digestate Landscape & Regeneration Horticulture Conclusions

3 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.

4 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

5 Market model Volume Product/Price Supply Sustainable Market Demand Location End user requirements

6 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

7 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

8 Demand - what end-users want Low risk Consistency CONFIDENCE/ TRUST Fitness for purpose

9 Demonstrating digestate safety and fitness for purpose Flavour/odour taints Clostridium botulinum Impact of pasteurisation on pests and diseases Compost/digestate data AD risk assessment Herbicides in digestate Odour/ammonium Biofertiliser matrix Food Standards Agency/Crop Assurance schemes e.g. Red Tractor

10 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

11 Why use digestate? Nutrients N, P, K, S, Mg Trace elements Can save money Reduce carbon footprint Organic matter (fibre) At present almost all digestate is used in agriculture - experiments under DC-Agri

12 Developing digestates 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

13 Other potential markets Brownfield site restoration soil improvement (growing energy crops) Soil manufacture Turf establishment Sports and amenity turf maintenance Horticultural applications

14 L & R Field experiments 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

15 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

16 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

17 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

18 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

19 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?

20 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

21 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

22 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

23 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

24 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

25 Pines No differences foliage quality good for all treatments And no significant differences in: Growth Quality Fresh weight Dry weight

26 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

27 Nitrogen availability The digestates contained 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)

28 Establishment Strawberries planted end of Jan 2013 Feeding started three weeks later Digestate (day 18) Control

29 Total fruit yield at harvest

30 Average fruit weight at harvest

31 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

32 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?

33 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

34 Tomatoes 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.

35 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.

36 Tomatoes Digestate dilutions FW1 FW2 CD Total-N (mg/l) Ammonium (mg/l) Nitrate (mg/l) Excess total-n (x) 38 (30)* 61 (48) 30 (23) Ammonium (% of total) 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 postflowering solutions.

37 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.

38 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

39 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

40 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

41 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

42 Thank you