CR-LU6
Sustainability Committee
Inquiry into Carbon Reduction in Wales: Rural Land Use Management and Carbon Reduction
Response from: Forestry Commission Wales
1. Is the proposed 3 per cent annual reduction target by 2011 'in areas of devolved competence'1 sufficient to enable Wales to make its full contribution to meeting UK-wide targets? If not, what targets should be put in place?
No specific comment.
2. Should the emission reduction target be based on Welsh consumption, or production, or both (ie should it take into consideration the carbon dioxide generated in Wales (production), or the carbon dioxide emissions that Wales'residents are responsible for, regardless of their source (consumption))?
No specific comment.
Response to questions specific to carbon dioxide reduction and rural land use management:
3. What particular challenges do rural land managers in Wales face in reducing carbon dioxide emissions from their activities, and how can these challenges be overcome?
At a strategic level, land management decisions are complex due to the multiple benefits and costs of a particular course of action. This is exemplified by the issue of carbon management, as almost every course of action imaginable, even actions designed to reduce carbon dioxide emissions, have a negative carbon footprint if considered too narrowly or over too short a period of time. The most realistic route through this myriad of interconnected relationships is to consider issues holistically using techniques such as life-cycle analysis and multi-criteria decision support processes.
However this presents the next, more technical, set of challenges which concern the evidence base to make holistic decisions. An example of this from a rural land use perspective is the incomplete science base around the dynamics of carbon fluxes from organic soils when trees are planted or harvested in relation to the longer-term positive impact on soil carbon of woodlands as a land-use. We have some information to inform decisions on these issues but not enough to support every potential option or scenario.
4. To what extent has the Welsh Assembly Government been successful in utilising the powers available to it in order to reduce carbon dioxide emissions from rural land use?
From a forest land use perspective, the Welsh Assembly Government has complete control over Welsh forestry policy. The Forestry Commission is currently managing the process of Woodland strategy review on behalf of the government and the requirement for carbon dioxide emissions reductions is a significant policy driver in this review.
5. What opportunities does the Welsh Assembly Government have to help rural land managers:
a. reduce their carbon dioxide emissions, and
b. better manage the storage of carbon within the land?
The faster provision of better underpinning science in terms of the specific operational impacts of disturbance on specific soil types under certain climatic conditions. The science base for forestry operational impacts is under development so generalities tend to be made about carbon fluxes across too broad a range of operations and soil types. This is especially important for forestry and wider habitat creation/restoration activities where carbon will be fixed or stored in the biomass accumulating on the site.
6. Could alternative targeting of Welsh Assembly Government financial resources lead to greater carbon dioxide emissions reductions within the context of rural land use than are currently being achieved? If so, where could additional resources lead to greatest impact? (Please provide detail to support your evidence).
The inquiry should take a wider perspective of the total carbon footprint from rural land use, as well as seeking to balance against other policy concerns such as food & energy security.
7. What examples from other administrations (devolved, UK, and overseas), where other means have been used to achieve reductions in carbon dioxide emissions from rural land use, could be adopted in Wales under current powers?
No specific comment.
8. In the context of the Government of Wales Act 2006, which further means of reducing carbon dioxide emissions from rural land use could only be achieved with the introduction of further legislative competence for the National Assembly for Wales?
No specific comment.
9. How can land managers in rural areas contribute towards the Welsh Assembly Government’s 3% reduction targets and how much reduction in CO2 in Wales could realistically be achieved through improved land management?
The inquiry as well as focusing on the carbon dioxide emissions reduction potential of land use also needs to consider the role of products from land use on non-land use related emissions. It needs to clarify the difference between conserving C stocks in the land and enhancing C sequestration (net uptake of C).
The obvious example from a forestry perspective is the substitution potential of harvested wood products, and of biomass for energy production.
Harvested wood products
Carbon is removed from the atmosphere during tree growth and dry wood is approximately one half carbon by weight. Some of this wood, and the carbon within it, can be harvested and turned into useful products. Carbon remains 'fixed' within these products throughout their useful lifespan and is only released back to the atmosphere if the wood is oxidised as a result of combustion or decomposition.
The dynamics of carbon in harvested wood
Harvested wood is used to make what may be referred to as primary products. When primary products come to the end of their useful lives, the wood may be reused in secondary products. Both primary and secondary wood products make a contribution to carbon dynamics.
The main processes that determine the carbon dynamics of harvested wood products are fundamentally different to those at work in forest ecosystems. The carbon content of the forest ecosystem depends on the balance between the process of photosynthesis and respiration by trees, the accumulation and loss of organic matter in soil, disturbances such as forest fires and windthrow, and interventions by humans (tree planting, thinning and deforestation). Most of these processes are biophysical. In contrast, C stocks and flows associated with wood products depend principally on socio-economic forces.
The size of a particular wood product pool is a direct consequence of the number of units of the product in use at a given time and the average amount of wood contained in individual units of the product. In principle, measures that encourage use of more wood products should result in C stocks in wood products increasing, so that C is sequestered in products. Quite a large proportion of the harvested wood has a relatively short lifespan, for example wood processing factories often burn a significant fraction of off-cut wood to provide heat and electricity for the manufacturing process. The remaining harvested wood goes to make longer-lived primary wood products in construction, insulation, packaging and fuel. Generally these will have service lifespans ranging from one or two years up to forty years. Exceptionally, primary wood products may remain in service for a100 years or more.
Modern house designs often involve relatively small amounts of structural wood, so by changing designs, the quantity of wood contained in a house could be increased.
It should also be noted that, as with trees, carbon sequestration in wood products is potentially reversible. If existing or new wood products are replaced with non-wood products at some point in the future, C stocks in wood products will decrease, with implied emissions of carbon to the atmosphere, if wood products taken out of use are burned or decay.
Carbon in secondary wood: bury, recycle or burn?
When people finish with a wood product, it can be buried in a landfill, recycled into a secondary product, or burned. These three options have different positive and negative carbon balance impacts and all require transport of wood, which requires energy.
When these are considered alongside other factors, often it is difficult to clearly distinguish the most environmentally beneficial option. Of the three options, the C dynamics of 'fixed' carbon are most simple for burning wood: C fixed in wood is released back to the atmosphere immediately. The mix of carbon-based gases released depends on how efficiently the wood is burned. If this is efficient, most of the carbon returns as
CO2. For less efficient cases (e.g. poorly tended open log fires), a proportion is returned as more complex hydrocarbons. The C dynamics of recycled wood products are similar to primary products - the main determining factor is the requirement for the particular product being manufactured. However, there is no clear picture about the interactions in consumption of virgin and recycled wood. Quite high uncertainty also surrounds the C dynamics of landfilled wood. The quantity of C in wood in landfill could be significant, but estimates are based on many assumptions and it is not clear if, when or by what process landfilled wood will decay.
Substitution potential
Harvesting trees reduces the carbon stock in the forest and thus reduces C sequestration, dependent on the use of the harvested tree and the regrowth at the site. The net quantitative change in forest C stock is affected by many environmental, biological, ecological and management variables. However, even if there is a net removal of C from the forest, it may help reduce C emissions from fossil fuel use through substitution, either directly (use as an energy source) or indirectly (through use in place of other, more energy intensive materials such as steel, bricks or concrete). In many instances, wood products may deliver multiple substitution benefits. For example, waste wood created when machining logs into products may be used as energy to drive the manufacturing process, or an article of furniture may be disposed of by burning and recovery of the energy.
Direct substitution: woodfuel
Several points about woodfuel use and its potential for substitution need to be made:
If forests regrow after harvest and re-fix C lost during woodfuel combustion and energy generation then potential emissions from fossil fuel combustion are avoided. Thus a sustainable cycle of woodfuel harvesting and forest re-growth continues to avoid fossil fuel C emissions. This is unlike measures to cause additional sequestration in forests, which reach saturation, determined by the environmental and forest characteristics at a site.
Bioenergy forests usually have lower carbon densities than forests managed less intensively, although if bio-energy plantations are established on e.g. farmland the carbon density may be higher.
The potential for woodfuel for direct substitution is determined by the biomass productivity.
The calculation of the net reduction in fossil fuel consumption avoided by bioenergy obviously needs to take into careful account the fossil fuel use in harvesting, processing and transport of woodfuel. However these are unlikely to be greater than for comparable fuels, most of which have high carbon extraction costs as well as tending to be transported long distances via heavily carbon-intensive infrastructure.
Indirect substitution: use of wood products
GHG emissions may also be reduced by using wood in place of other more energy expensive (and carbon-intensive) materials. This will only contribute to emission reduction if:
Product consumption patterns are actively modified,
Existing energy-intensive products are not replaced with wood products until end of life,
Opportunity for substitution of materials for particular products or uses is real, and that product life times are taken into account in the assessment,
Material substitution does not lead to creation of alternative markets for the materials not being used (i.e. 'leakage’).
There has been considerable work on the opportunities for materials substitution in the building industry, including Life Cycle Analysis (LCA), which attempts to account for the specific mix of GHG emissions arising from the use of different materials and methods of manufacture, the maintenance and disposal and the service life. Although the estimates show considerable variation, depending on the types of buildings assessed and the methodologies used, lower C emissions are associated with woodbased construction in all cases. A more recent study by ECCM has provided a 'carbon calculator’ for the building industry, using various emission factors for materials, for example from the BRE.
Broader context for these contributions from Forestry Commission Wales: Forest carbon fluxes
The annual total CO2 emissions for the UK were 544 Mt CO2 (provisional Defra figures for 2007). Therefore, even dramatic increases in the woodland area, in carbon stocks per area, in woodfuel substitution for fossil fuel energy and in timber substitution for carbon-intensive materials, will not make a major contribution to emissions reduction. However, as Kyoto commitments are for reductions in emissions of 12.5% of 1990 values (i.e. 74 Mt CO2), changes in the fluxes in CO2 and other GHGs into and from forests and forest activities could make a small, but significant contribution to the UK GHG balance.
The pattern of accumulation of carbon in a stand of trees over its life cycle reflects the growth of timber (the "increment”), since the dry weight of wood comprises 50% carbon (Matthews, 1993), and stem wood comprises a large part of tree biomass.
Models or tables providing forecasts of timber growth and yield of forests can thus be used to estimate carbon stocks and accumulation rates. Much empirical data has been collected on the characteristic time course of stemwood (or sometimes total biomass) accumulation within stands following planting or natural regeneration.
Successive inventories of the growing forest stand, or estimates based on growth and yield models such as BSORT, show increased carbon indicating that the stand is a sink and that there is carbon sequestration.
The time-course of carbon accumulation is generally sigmoid: the initially rate is relatively slow as the canopy develops (the 'establishment phase’), but generally accumulation accelerates until the 'full-vigour phase’ is reached. During this phase, a characteristic maximum rate of carbon accumulation is sustained for a number of years, the duration and magnitude of which is determined to a large extent by the combination of tree species, site characteristics (e.g. nutrient availability) and climatic conditions.
The full-vigour phase ends as tree sizes become so large that losses of carbon due to respiration, senescence and death, begin to approach carbon inputs from photosynthesis (the 'mature phase’). Net growth and carbon accumulation in the stand slows during this phase. Eventually the tree stand may reach a state where losses of carbon more or less balance the inputs (the 'old-growth phase’), and the tree stand becomes 'carbon-saturated’, with the stand carbon stock varying about a characteristic long-term average value. Small amounts of carbon may continue to accumulate in the soil, with the time for soil carbon to reach equilibrium being much longer than that for forest biomass, (Luyssaert et al. 2008, Nature).
The above leads to two important general points:
1. Planting a stand of trees on an area results in a change in the carbon density of that area. Carbon sequestration only occurs for a limited period while the carbon density is increasing, and the rate is at its maximum in the full vigour phase.
Stands of trees alone do not continuously and indefinitely sequester carbon from the atmosphere (but there may be continuous sequestration in soil).
2. The duration and rate of carbon accumulation during the full-vigour phase of growth are determined by a combination of tree species, site and management characteristics and climate. The magnitude of the average carbon density maintained during the over mature phase is also determined by these factors. If tree species, site types and climatic conditions are selected to maximise the duration and magnitude of carbon accumulation during the full-vigour phase, this may not necessarily (and indeed is quite unlikely to) result in a high average carbon density during the over-mature phase. It is probably more important to select tree species, site types and climatic conditions to maximise the carbon density ultimately attained.
The long-term carbon stocks estimated for different types of forestry systems fall into two distinct groups: those associated with some form of active management for production and those involving protection of woodlands to create ‘carbon reserves’.
Forest soils can contain more carbon than the trees, particularly the peat-based soils common in the upland areas of the UK (Broadmeadow & Matthews, 2003, FCIN48). The literature reviewed so far and the available SSR Programme data show that estimates of C content in forest soils can vary between 90 and 2500 t CO2eq ha-1.
In view of this context and for carbon inventory purposes we need to know more about the carbon stock in trees but especially that held in soil, in timber and other products. We also need to know more about the consequences of different management options for the carbon balance of forests to maximise the mitigation potential (see recent summary by Nabuurs et al. 2008). However there is general agreement over the four main strategies available globally:
(1) increasing forest area;
(2) increasing carbon content per unit area (so-called "carbon density” at stand and landscape scale;
(3) expanding use of forest products to substitute for carbon-intensive materials and fossil fuels; and
(4) reducing emissions from deforestation and degradation (Canadell & Raupach, 2008; Nabuurs et al. 2008).
These options are not mutually exclusive and all could be pursued in tandem although the relationship between (2) and (3) is more complex to manage. These two options offer most potential for Welsh forestry in helping to reduce or mitigate carbon dioxide emissions, with (1) also having some merit in the context of a delivering a wider set of sustainable development outcomes from increasing woodland area.
