Wood ash recycling in forests: opportunities and challenges

Paul Hazlett, Kirsten Hannam, Lisa Venier Natural Resources Canada - Canadian Forest Service

Sault Ste. Marie, Ontario Bio-heat Community of Practice Workshop, March 7, 2017

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

• Challenges - certain barriers

• Moving forward

Bioenergy production in Canada

National Energy Board. 2016.

Bioheat projects in Canada

OMECC, 2016.

Wood ash use internationally

Sweden: ‘Ash recycling should be done on sites where extensive amounts of harvesting residues are extracted at some point during the rotation period’ (Swedish

Forest Agency 2008)

Finland: ‘Logging residue can be cleared if the nutrient balance of the forest stand is maintained through the use of ash’ (TAPIO 2010)

United Kingdom: ‘…the removal of brash could be acceptable on all of the high risk soil types provided that the nutrients are replaced through… the application of limestone or wood ash’ (Forestry Commission 2009)

Amelioration of biomass harvested sites with wood ash waste: improving Canadian forest productivity and sustainability through an alternative approach to bioenergy waste management

Partners: Ontario Power Generation, Wood Pellet Association of Canada,

Tembec, CanFor Pulp, J.D. Irving, Resolute Forest Products, MNRF,

FP Innovations

Laurentian U, Lakehead U, U of Toronto, U of Northern British

Columbia, U of Manitoba, U of Quebec, U of Saskatchewan

http://cfs.nrcan.gc.ca/projects/140 (English) http://scf.rncan.gc.ca/projets/140?lang=fr_CA (French)

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

• Challenges - certain barriers

• Moving forward

Canadian bioenergy wood ash chemistry (pH 7 – 14)

Fly ash Bottom ash

Calcium (g/kg) 92 - 248 4 - 211

Magnesium (g/kg)

6 - 29 1 - 33

Potassium (g/kg)

14 - 91 1 - 51

Nitrogen (g/kg) 0.4 - 4 <0.01 - 3

Phosphorus (g/kg)

3 - 11 0.1 - 12

Soil pH and plant nutrient availability

% Sa Si Cl pH

LFH 3.9

Ae 68 26 6 4.0

Bm1 61 31 8 5.0

Bm2 79 16 5 5.2

C 94 2 3 5.3

Brady and Weil, 2002

nutrient compensation - “recycling of nutrients should be a fundamental principle in sustainable forestry” (Saarsalmi et al., 2001)

reduction in soil and surface water acidity - amending soils depleted of base cations (Ca, Mg, K) due to acid rain

fertilization of whole-tree and biomass harvested sites - enhancing forest productivity by raising soil pH

Potential environmental benefits of recycling ash in forests

Wood ash study sites

Number of papers 109

Number of sites 118

Number of countries 14

Biomes Boreal, temperate, Mediterranean

Stand ages Ranging from clearcuts to 100 year old stands

Wood ash studies - Europe

Wood ash studies – North America

Forest Floor pH

Ash granules (Emilsson 2006)

Hardened ash (Emilsson 2006)

Loose ash

Exchangeable calcium

Nutrient Availability

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

- increased soil pH

- increased nutrient availability

= ?

Fly Ash (mg/kg)

Bottom Ash (mg/kg)

Wildfire Ash (mg/kg)

Arsenic 4 - 28 <0.1 - 139 6

Cadmium 2 - 18 0.1 - 8 0.1

Copper 35 - 145 0.1 - 205 6

Lead 3 - 61 0.5 - 369 15

Zinc 389 - 2662 32 - 1504 500

http://www.msnbc.com/msnbc/washington-worst-wildfire-aftermath#slide1

Fire ash data from Maynard et al. 2014. Env. Rev.

Exchangeable calcium

Bioenergy ash application Wildfire and prescribed fire

FOREST FLOOR MINERAL SOIL

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

- effects on nutrient availability similar to wildfire?

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

• Challenges - certain barriers

• Moving forward

• Wood ash - AB • Soil amendment – BC (fly ash) • Waste - BC (bottom ash) • Industrial By-Product - NB • Biosolids - NS • Solid non-hazardous waste; Non-agricultural source material – ON • Fertilizing residual/Liming material – QC • Fertilizer – Canadian Food Inspection Agency • Liming agent - Canadian Food Inspection Agency • Compost - Canadian Council of Ministers of the Environment

(CCME)

In general, the use of wood ash as a soil amendment falls under provincial/territorial jurisdiction…

http://cfs.nrcan.gc.ca/publications/download-pdf/37781 (English) http://cfs.nrcan.gc.ca/publications/download-pdf/37782 (French)

soil pH increase, changes in soil N production/availability, increased N levels in soil and surface water

heavy metal contamination

impacts on vegetation and soil biodiversity - caustic

Potential environmental problems of recycling ash in forests

Ash-specific guidance needed?

• Ash pre-treatment

• Application timing and frequency

• Co-applications (urea; pulp and paper biosolids; lime; biotite)

• Dosage rate

Dosage rate comparisons

Europe Canada Austria 3 Mg/ha/50 years CCME: 200 Mg/ha/45 years

Denmark

0.5-7.5 Mg/ha/10 years Alberta: 45 Mg/ha/lifetime

Lithuania 5-6 Mg/ha/rotation Quebec: 88 Mg/ha/20 years

Sweden 3 Mg/ha/10 years; 6 Mg/ha/rotation

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

• Challenges – certain barriers

- regulatory approval process

- environmental impacts knowledge

- no Canadian guidance specifically for forests

Wood ash recycling in forests: opportunities and challenges

• Context

• Opportunities - possible benefits

• Challenges - certain barriers

• Moving forward

http://cfs.nrcan.gc.ca/projects/140 (English) http://scf.rncan.gc.ca/projets/140?lang=fr_CA (French)

Ash chemistry database Techno-economic analyses Canadian research sites

UNBC – USask – UManitoba – LakeheadU – CFS/MNRF – LaurentianU/UToronto/MNRF - UQAT/TELUQ

AshNet Research Sites AshNet contacts: paul.hazlett@canada.ca kirsten.hannam@canada.ca