Hedges for Heat. Rob Wolton February 2016

Transcription

1 Hedges for Heat Rob Wolton February 2016

2 Why manage hedges for woodfuel? Cheap, efficient, source of heat energy Help to improve hedge health Make hedges pay their way

3 What s a hedge? A multi-functional linear woodland which can provide: Great woodfuel crops Rich wildlife habitat Many ecosystem services

4 Farm woods or hedges for fuel? Hedges more accessible than woodlands. 4 parishes in Tamar Valley: 59% of available energy in hedges, 41% in small woodlands. Devon s hedges have same biomass as county s farm woodlands (<50 ha).

5 What hedges are suitable? Most types! More tree species the better Ash, willow, sycamore especially good Even pure hazel worthwhile

6 Expected yields from different hedge types

7 How to manage for fuel Avoid top cutting Side trimming OK Harvest at coppice stage optimal balance between yield, hedge health and wildlife Coppice cycle 15 to 20 years depends on species, exposure, fertility

8 Legal points Felling licence required for stems >15cm DBH if >5cum felled in 3 months (2cum if sold). Equal to 20 to 40 larger stems in hedge ready to coppice. For BPS claimants, must comply with GAEC 7 no coppicing between 1 May and 31 August. Hedge must be allowed to regrow, otherwise submit removal notice under Hedgerows Regulations to local panning authority.

9 Logs or woodchips?

10 Chips Logs Waste None 40% Handling All machine Much manual Specialist equipment? Whole tree chipper Wood processor optional Marketability Restricted to large houses, commercial properties Anyone with stove, boiler, etc Production cost assumes on farm production and use p per kwh 4-8p per kwh Boiler cost (35kW) 30,000 18,000

11 How much hedge do you need? To heat typical 4 bedroom leaky farmhouse (35MW hours) Woodchip: coppice m of hedge each year So, 3km of hedge needed (15-20 year coppice cycle) Logs: 50% more hedge needed Calculating tool available at

12 Harvesting techniques 1. Chainsaw plus hand dragging Hard manual work!

13 2. Chainsaw plus excavator with rake or fork Health and safety concerns

14 3. Tractor mounted circular saw Difficult to coppice in one stage Two tractors, or two operations required

15 4. Excavator plus felling head Chainsaw bar - risk of damage from stone, metal, etc Tree shears - can fracture stools

16 Harvesting methods compared Number of people Length of hedge coppiced in a day Cost of buying equipment (excluding tractor or excavator) Cost per metre Chainsaw 2 Under 50m Under 1, Chainsaw plus excavator Tractor with circular saw + tractor with rake/fork Excavator with tree shears 2 Over 250m 1,000 to 5, m 1,000 to 5,000 4 to m 200m 1,000 to 5,

17 Chip green or seasoned? Green Seasoned Chip quality Higher more even sized Lower more dust & shards Machinery wear and tear Lower softer wood Higher Drying Risk of mould Heap and allow to self-dry in well-ventilated shed takes 3-4 months Higher but if no green leaves still low Not necessary dried before chipping Lower Biomass loss 15% None, if no rot Aim for less than 30% moisture content. Key consideration is number of times material has to be handled between hedge and boiler.

18 Log processing Season on site or at yard aim for 20% moisture content Season faster if cut and split green Transport by trailer or forwarder Processing with chainsaw and axe/log splitter, or with wood processor

19 Branch logger Make use of small stem wood that would otherwise be wasted Seasons rapidly Multiple uses for product Produce marketable

20 Chip processing Chip quality needs to match requirement of boilers If for sale, likely to need to meet BSI standards Shards and splinters can be filtered out with sieves

21 Whole-tree drum-chipper, crane-fed Use for maximum efficiency. Machines heavy will cause rutting in wet conditions. Over 250m can be chipped in one day. 3 per metre. Expensive to purchase, hire and transport - ensure high volumes to chip or join forces with neighbours.

22 Hand-fed disc-chipper Slow and labour intensive 2 people can do m of hedge in a day Larger stem wood may need cutting up But for short hedge lengths (<75m) cost effective. 5 per metre

23 Green chips self dry! Takes 3-4 months Should not be turned No compost if no green leaves Aim for less than 30% moisture content.

24 Wildlife and landscape impact Woodfuel management better than repeated annual trimming or neglect In isolation, not ideal for wildlife Aim for landscape with wide variety of hedge structures

25 Environmental recommendations Manage less than 50% of hedges for fuel Coppice no more than 5% of hedges in one year Retain mature hedgerow trees especially those with veteran features Hedge management plan desirable!

26 Energy Costs compared, January 2016 p/kwh Hedge woodchips1 Heating oil Bought woodchips Mains gas Bought logs Coal LPG Hedge logs1 Pellets Electricity

27 Savings and grants Last bar chart did not consider: Savings from not trimming hedges 88p per metre per year Income from Environmental or Countryside Stewardship Renewable heat subsidies

28 Conclusions Crop multifunctional linear woodlands (hedges!) for fuel for: 1. Cheap heat 2. Green energy 3. Healthier hedges

29 Acknowledgements