1. Balancing green energy and materials recycling: woody biomass for combustion and green waste composting combined with compost for growing media? Vandecasteele Bart1, Boogaerts Christophe2, Vandaele Elke2 1 Institute for Agricultural and Fisheries Research (ILVO) 2 Vlaco npo

2. CURRENT SCENARIO GREEN WASTE
SYNECO SCENARIO GREEN WASTE
Woody biomass for combustion?
Fine fraction for AD?

3. Experimental set-up Full-scale composting experiments:
Green waste composting
9 compost facilities
3 periods during 1 year
2 scenarios: regular versus experimental
3 fractions: woody biomass, feedstock for composting and compost

4. Green waste Regular Experimental Woody biomass Sieving Compost
Feedstock
Composting
Sieving
Compost
Green waste
Experimental
Feedstock
Sieving
Woody biomass
Composting
Compost

5. Quality assessment Process: °C, turning frequency, …
Organic matter (OM) and total nutrients, C/N, C/P
Woody biomass:
gross calorific value
stones & impurities
Cl and S
Feedstock and compost: biochemical composition
Compost:
Waterextractable and plant-available nutrients
N immobilisation
OUR
pH, EC, germinable seeds

6. Effect of period during the year
Regular
Green waste collected in Summer vs. Winter and Spring:
Lower % OM, higher nutrient content

7. Effect on the green waste feedstock
Regular versus experimental
Green waste collected in:
Spring: clear effect
Lower % OM: 47 vs. 73 %OM/DM
Higher nutrient content
Summer: small effect
Winter: small effect

8. Effect on recovered woody biomass
Regular versus experimental
Green waste collected in:
Spring: small effect
Summer: small effect
Winter: small effect

9. Effect on compost quality
Regular versus experimental
Green waste collected in:
Spring: small effect
Summer: small effect
Winter:
slightly lower % OM: 32.2 vs %OM/DM

10. Effect on compost quality (2)
Positive correlation between N immobilisation in the compost and Oxygen Uptake Rate (= microbial activity)

11. Changing the composting process
Experimental composting: more intensive process
Higher turning frequency = faster process but higher operational costs
Composting periods (excluding the curing phase and storage) can be reduced to:
minimum 15 weeks
for static piles turned fortnightly
for static piles turned at least once a month but with an initial tunnel composting or with forced aeration
minimum 10 weeks
for windrow composting with weekly turning.

12. Added-value composts for growing media
Lab-scale experiments with sieving out the fine fraction < 0.5 mm
16 composts based on material collected in spring, i.e.; the compost with the highest organic matter content
Matrix EC
Dry matter
Org. matter
µS/cm
%/fresh
%/DM
unsieved
580 69 33 23
sieved
536 64 44 28
P-value t-test
0.16
0.000

13. Conclusions
Seasonal effect on biochemical composition of green waste feedstock and compost
Intensive composting compensated for extracting woody biomass from the feedstock
For green waste collected in summer extraction of woody biomass is not advised
N immobilization in compost was positively correlated with microbial activity
Use in growing media: high OM content by sieving out the fine fraction

14. More information? Vandecasteele, B., Boogaerts, C., Vandaele, E Combining woody biomass for combustion with green waste composting: effect of removal of woody biomass on compost quality. Waste management /j.Wasman