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Life-Cycle Energy and Carbon Implications of Wood-Based Products and Construction
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Forests can be an important element of an overall strategy to limit the atmospheric concentration of carbon dioxide (CO2) that contributes to climate change. As an integral part of the global carbon cycle, forests remove CO2 from the atmosphere as they grow, and accumulate carbon in tree biomass. Using wood products made from sustainably managed forests can reduce net CO2 emission by substituting in place of fossil fuels and energy-intensive materials. In this thesis the mechanisms by which wood product substitution can affect energy and carbon balances are studied. These include: the energy needed to manufacture wood products compared with alternative materials; the avoidance of industrial process carbon emission from e.g. cement manufacture; the use of wood by-products as biofuel to replace fossil fuels; and the physical storage of carbon in forests and wood materials.

A methodological framework is first developed by integrating knowledge from the fields of forestry, industry, construction, and energy. A life cycle perspective is employed encompassing the entire product chain from natural resource acquisition to material disposal or reuse. Analytical challenges that are addressed include the functional unit of comparison, the fossil reference system, land use issues of wood vs. non-wood materials, and the diverse phases of the product life cycle. The methodology is then applied to two multi-storey wood-framed buildings in Sweden and Finland, compared with two functionally equivalent buildings with reinforced concrete structural frames. The results show that less primary energy is needed to produce the wood-framed buildings than the concrete-frame buildings. CO2 emission is significantly lower for the wood-frame buildings, due to reductions in both fossil fuel use and cement calcination process emission. The most important single factor affecting the energy and carbon balances is the use of biomass by-products from the wood product chain as biofuel to replace fossil fuels. Over the life cycle of the wood-framed buildings, the energy of biomass residues from forest operations, wood processing, construction and demolition is greater than the energy inputs to produce the materials in the buildings. Realisation of this benefit is facilitated by integrating and optimising the biomass and energy flows within the forestry, industrial, construction, energy, and waste management sectors.

Different forest management regimes are studied in an integrated carbon analysis to quantify the carbon flows and stocks associated with tree biomass, soils, and forest products. Intensified forest management that produces greater quantities of biomass leads to net CO2 emission benefits by augmenting the potential to substitute for fossil fuels and non-wood materials. The increased energy use and carbon emission required for the more intensive forest management, as well as the slight reduction in soil carbon accumulation due to greater removal of forest residues, are more than compensated for by the emission reduction due to product substitution. Carbon stock changes in forests and wood materials can be temporarily significant, but over the building life cycle and forest rotation period the stock change becomes insignificant. In the long term, the active and sustainable management of forests, including their use as a source for wood products and biofuels, allows the greatest potential for reducing net CO2 emission.

Implementation issues related to the wider use of wood-based materials to reduce energy use and carbon emission are also explored. An analysis of the effects of energy and taxation costs on the economic competitiveness of materials shows that the cost of energy for material processing, as a percentage of the total cost of finished material, is lower for wood products than for other common non-wood building materials. Energy and carbon taxation affects the cost of wood products less than other materials. The economic benefit of using biomass residues to substitute for fossil fuels also increases as tax rates increase. In general, higher taxation of fossil fuels and carbon emission increases the economic competitiveness of wood construction. An analysis of added value in forest product industries shows that greater economic value is added in the production of structural building materials than in other uses of forest biomass. Co-production of multiple wood-based products increases the total value that is added to the biomass produced on an area of forest land. The results show that production of wood-based building material is favoured economically by climate change mitigation policies, and creates high added value within forest product industries.

Abstract [sv]

Skogsresurser kan utgöra en viktig del i en strategi för att begränsa koncentrationen av koldioxid (CO2) i atmosfären och därmed begränsa klimatförändringarna. Skog tar upp CO2 från atmosfären när den växer och kolet lagras i trädens biomassa. Trädprodukter från hållbart brukade skogar kan minska nettoutsläppen av CO2 genom att de kan ersätta fossilt bränsle och energiintensiva material. I denna avhandling studeras faktorer som påverkar energi- och kolbalanser när träprodukter ersätter alternativa produkter. Signifikanta faktorer är den energi som behövs för att framställa träprodukter jämfört med alternativa produkter, utsläpp av CO2 från industriella processer som vid cementproduktion, ersättning av fossilt bränsle med trärester samt lagring av kol i skog och träprodukter. En metodik har utvecklats för att studera dessa faktorer genom att integrera ämneskunskaper från byggkonstruktion, energi, industri och det skogliga området. Den bygger på ett livscykelperspektiv och innefattar hela material- och produktkedjor från naturresurs till avfall eller återanvändning av material eller produkter. De metodikfrågor som varit i fokus är den funktionella enheten för jämförelser, det fossila referenssystemet, utnyttjande av skogmark vid produktion av träprodukter samt produktens olika faser under en livscykel. Metodiken har sedan använts för att jämföra ett svenskt och ett finskt flervåningshus i trä med två funktionellt likvärdiga hus med betongstomme. Resultaten visade att det behövs mindre primärenergi för att tillverka trähuset än betonghuset. Energin som kan utvinnas från biprodukter under en träbyggnads livscykel – från skogsskötsel, förädling, konstruktion och rivning – är större än den energi som krävs för att tillverka byggnadsmaterialet i byggnaden. Nettoutsläppen av CO2 från både fossil primärenergi och cementkalcinering är också väsentligt lägre för trähuset, men användningen av biprodukter från skogsavverkning, träförädlingskedjan och rivningsvirke för att ersätta fossilt bränsle har störst påverkan på kolbalansen. För att fullt ut tillgodogöra sig biprodukters potentiella fördelar krävs att de olika sektorerna för skogsbruk, industri, konstruktion, energi och avfallshantering integreras och optimeras med avseende på energi- och materialflöden.

Olika skogsskötselmetoder har analyserats för att kvantifiera de flöden och den lagring av kol som sker i biomassa, mark och träprodukter. Intensifierat skogsbruk gav mindre utsläpp av CO2 per ha skogsmark, eftersom potentialen ökade för att ersätta fossila bränslen och energiintensiva material. Denna substitutionseffekt kompenserade mer än väl för den ökning i energianvändning och de utsläpp av CO2 som den intensivare skogsskötseln medförde, inklusive för den minskning av lagrat kol i marken som uttaget av skogsrester medförde. Lagring av kol i skogar och träprodukter kan vara intressant i ett kort tidsperspektiv, men under en byggnads livscykel och ett skogsbestånds rotationsperiod har den liten betydelse. I längden uppnås den största minskningen av CO2-utsläpp genom en aktiv och hållbar skogsskötsel med uttag av skogsresurser för användning till träprodukter och energi.

I denna avhandling studerades också hur användningen av träprodukter påverkas av energi- och miljöskatter. En analys av energi- och skattekostnadernas effekt på konkurrenskraften för trämaterial visade att energikostnaden är lägre för trämaterial än för andra vanliga byggmaterial. Energi- och koldioxidskatter påverkar träprodukter i mindre utsträckning än produkter i andra material. De ekonomiska fördelarna av att använda biomassa som ersättning för fossila bränslen ökar också med höjda skatter. Konkurrensfördelarna för träkonstruktioner ökar därför generellt i takt med högre skatt på fossila bränslen och CO2-utsläpp. En analys av förädlingsvärdet hos skogsprodukter visade på en större värdeökning vid produktion av byggnadsmaterial än för andra biomassebaserade produkter. Samproduktion av flera träprodukter ökade det totala värdet hos biomassan per skogsareal. Resultaten visade att produktion av träbaserade byggnadsmaterial får ekonomiska fördelar av klimatpolitiska åtgärder och att sådan produktion har ett högt förädlingsvärde för industrierna i träbranschen.

Place, publisher, year, edition, pages
Sundsvall : Mid Sweden Univ , 2007.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 34
Keyword [en]
forest products, climate change mitigation, carbon balance, energy, life cycle, wood, land use
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:miun:diva-50ISBN: 978-91-85317-67-7 (print)OAI: oai:DiVA.org:miun-50DiVA: diva2:2032
Public defence
2007-11-23, G2355, Östersund Campus, Östersund, 13:00 (English)
Opponent
Supervisors
Available from: 2007-12-20 Created: 2007-12-20 Last updated: 2009-02-13Bibliographically approved
List of papers
1. Carbon dioxide balance of wood substitution: comparing concrete- and wood-framed buildings
Open this publication in new window or tab >>Carbon dioxide balance of wood substitution: comparing concrete- and wood-framed buildings
2006 (English)In: Mitigation and Adaptation Strategies for Global Change, ISSN 1381-2386, E-ISSN 1573-1596, Vol. 11, no 3, 667-691 p.Article in journal (Refereed) Published
Abstract [en]

In this study a method is suggested to compare the net carbon dioxide (CO2) emission from the construction of concrete- and wood-framed buildings. The method is then applied to two buildings in Sweden and Finland constructed with wood frames, compared with functionally equivalent buildings constructed with concrete frames. Carbon accounting includes: emissions due to fossil fuel use in the production of building materials; the replacement of fossil fuels by biomass residues from logging, wood processing, construction and demolition; carbon stock changes in forests and buildings; and cement process reactions. The results show that wood-framed construction requires less energy, and emits less CO2 to the atmosphere, than concrete-framed construction. The lifecycle emission difference between the wood- and concrete-framed buildings ranges from 30 to 130 kg C per m2 of floor area. Hence, a net reduction of CO2 emission can be obtained by increasing the proportion of wood-based building materials, relative to concrete materials. The benefits would be greatest if the biomass residues resulting from the production of the wood building materials were fully used in energy supply systems. The carbon mitigation efficiency, expressed in terms of biomass used per unit of reduced carbon emission, is considerably better if the wood is used to replace concrete building material than if the wood is used directly as biofuel.

Keyword
biofuels, biomass, building materials, carbon dioxide, concrete, forest industry, greenhouse gas balance, wood
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-401 (URN)10.1007/s11027-006-7207-1 (DOI)2-s2.0-33746528643 (Scopus ID)
Available from: 2008-11-18 Created: 2008-11-18 Last updated: 2016-09-29Bibliographically approved
2.
The record could not be found. The reason may be that the record is no longer available or you may have typed in a wrong id in the address field.
3. Energy and carbon balances of wood cascade chains
Open this publication in new window or tab >>Energy and carbon balances of wood cascade chains
2006 (English)In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 47, no 4, 332-355 p.Article in journal (Refereed) Published
Abstract [en]

In this study we analyze the energy and carbon balances of various cascade chains for recovered wood lumber. Post-recovery options include reuse as lumber, reprocessing as particleboard, pulping to form paper products, and burning for energy recovery. We compare energy and carbon balances of chains of cascaded products to the balances of products obtained from virgin wood fiber or from non-wood material. We describe and quantify several mechanisms through which cascading can affect the energy and carbon balances: direct cascade effects due to different properties and logistics of virgin and recovered materials, substitution effects due to the reduced demand for non-wood materials when wood is cascaded, and land use effects due to alternative possible land uses when less timber harvest is needed because of wood cascading. In some analyses we assume the forest is a limiting resource, and in others we include a fixed amount of forest land from which biomass can be harvested for use as material or biofuel. Energy and carbon balances take into account manufacturing processes, recovery and transportation energy, material recovery losses, and forest processes. We find that land use effects have the greatest impact on energy and carbon balances, followed by substitution effects, while direct cascade effects are relatively minor.

Keyword
Material balance, Recycling, Carbon dioxide, Material recovery, Manufacturing process, Biofuel, Biomass, Forests, Logistics, Wood fiber, Energy recovery, Combustion, Paper industry, Pulping, Particleboard, Reprocessing, Reuse, Building timber, Carbon balance
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-403 (URN)10.1016/j.resconrec.2005.12.008 (DOI)000238299900003 ()2-s2.0-33646565297 (Scopus ID)3383 (Local ID)3383 (Archive number)3383 (OAI)
Available from: 2008-11-18 Created: 2008-11-18 Last updated: 2016-09-28Bibliographically approved
4. Integrated carbon analysis of forest management practices and wood substitution
Open this publication in new window or tab >>Integrated carbon analysis of forest management practices and wood substitution
Show others...
2007 (English)In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 37, no 3, 671-681 p.Article in journal (Refereed) Published
Abstract [en]

The complex fluxes between standing and harvested carbon stocks, and the linkage between harvested biomassand fossil fuel substitution, call for a holistic, system-wide analysis in a life-cycle perspective to evaluate the impacts offorest management and forest product use on carbon balances. We have analysed the net carbon emission under alternativeforest management strategies and product uses, considering the carbon fluxes and stocks associated with tree biomass,soils, and forest products. Simulations were made using three Norway spruce (Picea abies (L.) Karst.) forest managementregimes (traditional, intensive management, and intensive fertilization), three slash management practices (no removal, removal,and removal with stumps), two forest product uses (construction material and biofuel), and two reference fossilfuels (coal and natural gas). The greatest reduction of net carbon emission occurred when the forest was fertilized, slashand stumps were harvested, wood was used as construction material, and the reference fossil fuel was coal. The lowest reductionoccurred with a traditional forest management, forest residues retained on site, and harvested biomass was used asbiofuel to replace natural gas. Product use had the greatest impact on net carbon emission, whereas forest management regime,reference fossil fuel, and forest residue usage as biofuel were less significant.

National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-404 (URN)10.1139/X06-257 (DOI)000248083800015 ()2-s2.0-34547939166 (Scopus ID)4293 (Local ID)4293 (Archive number)4293 (OAI)
Note

VR-Biology

Available from: 2008-11-18 Created: 2008-11-18 Last updated: 2016-09-26Bibliographically approved
5. Effects of energy and carbon taxes on building material competitiveness
Open this publication in new window or tab >>Effects of energy and carbon taxes on building material competitiveness
2007 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 39, no 4, 488-494 p.Article in journal (Refereed) Published
Abstract [en]

The relations between building material competitiveness and economic instruments for mitigating climate change are explored in this bottom-up study. The effects of carbon and energy taxes on building material manufacturing cost and total building construction cost are modelled, analysing individual materials as well as comparing a wood-framed building to a reinforced concrete-framed building. The energy balances of producing construction materials made of wood, concrete, steel, and gypsum are described and quantified. For wood lumber, more usable energy is available as biomass residues than is consumed in the processing steps. The quantities of biofuels made available during the production of wood materials are calculated, and the cost differences between using these biofuels and using fossil fuels are shown under various tax regimes. The results indicate that higher energy and carbon taxation rates increase the economic competitiveness of wood construction materials. This is due to both the lower energy cost for material manufacture, and the increased economic value of biomass by-products used to replace fossil fuel.

Keyword
Building materials, Economic competitiveness, Energy tax, Carbon tax, Wood products, Concrete, Steel, Bioenergy, Climate change mitigation
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-405 (URN)10.1016/j.enbuild.2006.09.005 (DOI)000244971500011 ()2-s2.0-33846924513 (Scopus ID)4292 (Local ID)4292 (Archive number)4292 (OAI)
Note

VR-Economics

Available from: 2008-11-18 Created: 2008-11-18 Last updated: 2016-10-04Bibliographically approved
6. Process-based analysis of added value in forest product industries
Open this publication in new window or tab >>Process-based analysis of added value in forest product industries
2009 (English)In: Forest Policy and Economics, ISSN 1389-9341, E-ISSN 1872-7050, Vol. 11, no 1, 65-75 p.Article in journal (Refereed) Published
Abstract [en]

Manufacturing products with greater added value is increasingly viewed as a strategic goal of forest products industries. Added value is defined here as the difference in economic value between the physical inputs and outputs of a production process, and is generally analysed at the firm or national economy level. In this study we identify and discuss issues involved in quantifying added value at the industrial process level, and develop a bottom-up method to estimate the value added by forest industry processes. We calculate the value added by 14 traditional and emerging processes within the Swedish forest products industries, and express the results using various indices. We find that the type of biomass input strongly influences the potential for adding value, with sawlogs allowing more added value and being less sensitive to input price fluctuations than pulpwood and forest residues. Structural wood products such as lumber and glue-laminated beams are found to give the greatest value added. Co-production of multiple products from a single raw material increases total value added. Integrating the value chain of pulp and paper production significantly increases the value added to pulpwood. Multiple conversion processes exist for using forest residues as fuel, with a range of potential added value. Consideration of the climate benefits of forest product use, through the application of a carbon tax, significantly increases the added value.

National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-406 (URN)10.1016/j.forpol.2008.09.003 (DOI)000262206600009 ()2-s2.0-56949088839 (Scopus ID)
Available from: 2007-12-20 Created: 2007-12-20 Last updated: 2016-09-23Bibliographically approved

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