Bufferstrips for biomass production

Bufferstripsfor biomass production

Ben Christen, University of Aarhus, Denmark

Contents

• Background• Buffer function and designs • Establishment• Performance• Policy development

Background

• Water Framework directive requires ’good eclogical status’ by 2015/2027

• Danish ’Plans for the aquatic environment III’ aim to further reduce nitrate pollution by 30%

• Bioenergy policy ’Grøn Vækst’ (green growth) opens lake shores and stream banks

• 5000 miles of watercourses• Production potential >100,000 tonnes/a

Buffer design and function

All Buffer Types• N-removal: 30-99%• P-removal: 20-99%• Pesticide removal: 10-

100% mainly dependent on width

Most suitable layout for biomass production identified:3-zone structure with grass, short rotation forestry + undisturbed zone

Grass strip

Function• Slows and spreads runoff• Filters sediment• Resists erosion by rill

flow• Takes up nutrients

during growing season• Denitrification

Production potential• Biomass for bioenergy

(6-16 t/DM/a)• Hay and silage• Pasture for extensive

grazing• Biogas feedstock

Short rotation forestry zone

Function• Infiltration of water

passing through grass strip

• Captures fine sediment• Removes pesticides• Immobilises nutrients• Denitrification

Production potential• Woodchips (5-14

t/DM/a)• Firewood (5-8 m3/a)• Pulpwood• Timber for higher value

uses

Undisturbed zone

Function• Reduces bank erosion• Protects buffer structure

in flood events• Buffers maintenance and

harvest operations in other two zones

• Enhancement of stream ecology (shade, debris)

Production potential• Occasionally timber of

larger dimensions but low quality

Buffer design variants

Fast BioenergyMiscanthus, reed canary grass, willow, alder, poplar

Higher value timberGrass mixture, bird cherry, oak, field maple, hornbeam, lime

Buffer design variants continued

Gentle slopeReed grass or grass mixture, alder, birch, field maple, poplar

10% slopeGrass mixture, birch, field maple, pear, black locust, alder

Buffer design variants - drainage

Drains broken by ditch before reaching buffer stripReed grass, alder, poplar, downey birch, elm

Establishing a productive buffer

Landscape impact projection

Planning

Ditch Grass strip Grey and red alder

Construction – May 2011

Establishment

Performance forecastTree species Latin name Age of max. mean

annual increment a

Max. mean annual increment m3 ha-1

Mean DM wood density kg/m3

Max. mean annual t DM

ha-1

Field Maple Acer campestre L. 15-25 7 750 5,3Sycamore Acer pseudoplatanus L. 30 11 590 6,5

Black Alder Alnus glutinosa L. 15-20 15.5 490 7,6Grey alder Alnus incana L. 12-16 18.5 490 9,1

Green Alder Alnus viridis L. Unknown b 5 570 2,9Silver Birch Betula pendula L. 15-30 11 630 6,9

Downey Birch Betula pubescens L. 15-30 8 680 5,4Hornbeam Carpinus betulus L. 20-30 5 770 3,9

Common Ash Fraxinus Excelsior L. 40-50 7 670 4,7

Poplar hybridsPopulus deltoides L. based

and other hybrids Unknown c 39 410 16

Aspen Populus tremula L. unknown 16 450 7,2

Aspen hybrids Populus tremula L. based unknown 23 450 10,3

Bird Cherry Prunus avium L. 30 9 580 5,2Common pear Pyrus communis L. 10-15 7 680 4,8

Pendunculate OakSessile Oak

Quercus robur L.Quercus petraea L. 40 7 670 4,7

Red oak Quercus rubra L. 25 8 670 5,4Black Locust Robinia pseudoacacia L. 15 11 730 8,0

Willow hybrids Salix viminalis L. based and other hybrids Unknown d 27 520 14,0

Lime Tilia cordata L.Tilia platyphyllos L.

30 11 520 5,7

White Elm Ulmus laevis L. 20-25 7 640 4,5

EconomicsBuffer land use types Overall Overall

In rotation Grass/clover a Pasture SRC SRF b Undisturbed c Energy balance Gross Margin

Production system (% of area): (MJ/ha/yr) (approx. £/ha/yr)

Winter wheat d 100% 150 500

A) High energy yield 30% 35% 35% 104 240

B) High energy yield + drainage ditch 35% 35% 30% 76 245

C) Multipurpose, intermediate slope 30% 55% 15% 66 150

D) Multipurpose, pronounced slope 50% 25% 25% 48 200

E) Extensive, steep slope 20% 70% 10% 74 130

F) Extensive, slope independent 70% 20% 10% 53 265

G) Woodland, slope independent 90% 10% 83 76

Key figures:

Dry matter yield (t DM/ha/yr) 10 8 5 9 6 0

Energy yield (MJ/ha/yr)e 170 90 55 150 100 0

Energy input (MJ/ha/yr) 20 14 5 10 8 0

Energy Balance (MJ/ha/yr) 150 76 50 140 92 0

Gross margin (DKK/ha/yr) 4500 4000 3000 1500 750 0

Policy development:Fuzzy Cognitive Mapping (FCM)• Procedure to involve

different stakeholders in a research or management process

• Method to extract, depict and analyze different kinds of knowledge

• Way to put academic, regulatory and practical knowledge on equal footing in an expert network

FCM-how-toExample question: Why do tourists come to Scotland and

how does that affect rural development?

Concepts

-pristine wilderness-wildlife-salmon fishing-grouse moor management-golf courses-forestry-rural employment-transport infrastructure-…

Pristine wilderness

Wildlife

Salmon fishing

Golf courses

Grouse moor management

Forestry

Rural employment

Transport infrastructure

An expert networkfrom the CREW Workshop, 03.11.11

Policy impacts derived