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Estimating Woody Biofuel Supply
Ademe Woody Biofuel / Objectives and Methodology / Objectives
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Objectives and Methodology




1) Objectives of the study

2) Links with other national studies on biomass carried out in 2008-2009

3) Consulting regional actors

4) Domain of application for the results

4.1) Constraints taken into account
4.2) Constraints not taken into account

5) Guarantee of accuracy for published results

This study is based on the latest available data. At a national scale, the objectives are to:

A. Improve calculations of available woody biomass:

  • in forested areas: by expanding previous knowledge, improving methods used to calculate available resources, applying IFN data collected between 2005 and 2007;
  • in non-forest wooded areas: poplar plantations, hedgerows and alignment trees, other woody resources in rural or urban areas;
  • according to potential uses of the woody resource (defined based on physical and qualitative criteria).

B. Better describe the availability of woody resources and better estimate the real volume of available resources in forests, poplar plantations and hedgerows by taking more constraints into account:

  • technical conditions for harvesting: physical accessibility of the resource;
  • cost-effectiveness: availability at a given price threshold;
  • sustainable management of the resource: availability considering soil sensitivity to mineral loss caused by removing small branchwood;
  • current harvesting volumes: evaluation of additional available resources.

C. Analyse available woody biomass from "secondary" resources (vineyards, orchards, urban trees, forest stumps) :

  • quantitative assessment of total availability;
  • assessment of the technical and economic feasability of harvesting the resources;
  • discussion of the environmental interests and limitations of harvesting the resources.

D. Create an Internet site to make the study results accessible.

Note: Our study was carried out in response to a request by the French government and provides a framework at the national scale. Our results are not appropriate for directly calculating the available wood supply for a given heating plant, for example. To define a supply plan at the local scale, the estimates provided by this study must be coupled with a detailed analysis of locally available technical and economic data.

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Several national surveys of the woody biomass available for energy production have recently been carried out at the request of the ADEME (2005 and 2009) and the MAAP (2007 and 2009). These surveys aim to:

  • enlarge the type of resources included (for example, hedgerows);
  • refine calculation methods (for example, with more detailed analyses in mixed forests);
  • improve scientific knowledge (for example, by evaluating small branchwood volumes);
  • take into account technical, economic and environmental constraints (physical accessibility, harvesting costs, nutrient loss in soils due to removing woody debris).

The two studies in 2008-2009 requested by the ADEME (entrusted to a collaborative team from the IFN/FCBA/SOLAGRO) and by the MAAP (entrusted to the Cemagref, with collaboration from the IFN) not only benefited from recent progress in knowledge and methodology, but also further contributed to that progress. The research on forest resources was carried out in close collaboration. Data, methods and hypotheses were shared or commonly defined in order to ensure coherent published results. The results for global available forest resources are the same for both studies for at least one scenario in the MAAP study. However, the results expressed in net availability reflect different objectives: where the MAAP study defines accessibility in technical terms (slope, etc.), the ADEME study includes both technical and economic considerations.

The diagramme below summarises the recent research evaluating potential woody biofuel resources. It also shows the links established between the ADEME and MAAP studies.

The 2009 studies also benefited from the ANR, most notably through the ECOBIOM project (PNRB programme on bio-energies) completed in 2009.

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In the framework of the study, five inter-regional meetings were organised at the beginning of 2009 to address local issues (minutes can be downloaded by clicking on "Archives and Downloads").

These meetings made it possible to inform the regional actors of the studies being conducted at the national scale and to better include regional specificities in the assessment of available resources, in particular by adjusting calculation hypotheses.

Any information relevant to forests was passed on the Cemagref for inclusion in the MAAP study.

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The study conducted an assessment at the national scale of the woody biomass available as a new source of energy. Resources of sawnwood, veneer-quality wood and construction wood were excluded from the assessment.

The figures published should be viewed as estimates in that they result from calculations based on hypotheses and currently available data. Furthermore, the study is oriented toward the national scale; therefore, not all regional specificities were taken into account. The regional results presented should be taken as likely approximations.

Initially, the figures estimated for each category of woody resource correspond to global availability, which may be equated to maximum harvestable volumes. However, different types of constraints can have an impact on the exploitability of these resources.

4.1) Constraints taken into account:

  • Sustainability: Removing certain types of biomass (small branchwood, stumps) may be detrimental to soil fertility through a loss of mineral nutrients. Degree of soil sensitivity to mineral loss was therefore taken into account for the sites in this study;
  • Physical accessibility: It is sometimes impossible to access stands or extract the harvest (steep slopes, no access for heavy equipment or self-loading lorries, etc.). Availability was classified according to difficulty of access;
  • Economic constraint: This is a fundamental constraint, the degree of which varies according to the income obtained from the harvested products. Today, we define a harvestable site as one which is profitable. Since harvesting costs vary with the degree of technical difficulty, if the price paid for a given resource increases, certain sites which were previously not profitable become so. The sites in our study are therefore classified according to harvesting cost, which determines their availability at a given price level.

4.2) Constraints not taken into account:

We were not able to include all potential harvesting limitations in our statistical approach since sufficient knowledge and consolidated information at the national scale are lacking for the moment.

  • Ownership patterns for private forests and willingness on the part of the owners to put wood up for sale were excluded from our analyses. Current knowledge and data are insufficient to model forest-owner behavior patterns at a national scale;
  • Available volumes concern saleable wood and not merchantable wood. Transportation costs have not been included due to a lack of precision at the national scale concerning regional locations of transformation sites and/or consumer centres for local woody resources. That is why road restrictions (bridges, weight limitations, hair-pin turns) were not analysed;
  • As for environmental constraints, not enough information was available at the time of the study to enable us to include soil sensitivity to compaction caused by heavy equipment. Harvesting restrictions in protected areas were also not included since such restrictions may be set on a site-by-site basis.

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Estimated values are displayed only when the inventory results they are based on have sufficient statistical accuracy (forested surface area or hedgerow length).

With three years of annual IFN survey data, sufficiently precise estimates for forested surface area are obtainable with 50 inventory points, resulting in 20,000 ha in poplar plantations and 36,000 ha in forests. For hedgerows, the minimum length required to determine accurate publishable results has been set at 20,000 km. These minimum threshold surface areas and lengths will be reduced as data becomes available from the first five annual IFN surveys. This approach reduces the uncertainty of the published results and guarantees that the estimates are based on actual physical resources. However, the uncertainty linked to other sources of data, models and hypotheses was not directly calculated. In such cases, the sensitivity of our results to variations in the main hypotheses was analysed.

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