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Estimating Woody Biofuel Supply
Ademe Woody Biofuel / Frequently Asked Questions
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Frequently Asked Questions

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CONTENTS:

A) Methods, hypotheses and results

B) How to use the Internet site


Last update: november 2009


A. Methods, hypotheses and results:

1. Which woody resources were analysed in the study?

2. What geographic resolution is available for the study results? How accurate are the results?

3. How are the ADEME and MAAP 2009 biomass studies linked?

4. What types of wood are potential sources of energy according to the study?

5. Can the study results provide enough information to define an energy supply plan for an industrial site?

6. Were the consequences of the Klaus wind storm (24 January, 2009) taken into account for the Aquitaine region?

7. Were recent objectives to increase harvest volumes taken into account in the economic evaluation?

8. How were woody resources in protected areas calculated?

9. Harvesting of private forest resources may be limited by fragmentation and a reticence to sell on the part of some land owners. Were these factors taken into account?

10. Was road access taken into account in the evaluation of available resources?

11. Were social and environmental criteria included in the evaluation of available fuelwood resources in hedgerow regions?

12. How were prices calculated for standing wood and wood decked at roadside?

13. The price of wood delivered to the site (factory or heating plant) is crucial for industrialists. Has this price been estimated?

14. Was the sensitivity of the economic model tested at the forest management scale in some areas?

15. Some current silvicultural operations result in lost woody resources (pre-commercial thinnings, clearing coppice from stands). How was this type of woody biomass included in the study?

16. Does using grape vine wood as a source of energy cause any special problems?


B. How to use the Internet site:

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Question 1 : Which woody resources were analysed in the study?

Forests, poplar plantations, hedgerows, alignment trees, isolated trees, vineyards, orchards, heathland and scrubland trees and urban trees were included in the study. Stumps remaining in the forest after harvesting were also included. We excluded any area where food crops could be produced: agricultural cropland, grassland and meadows. Areas specifically cultivated to produce biofuels (very short rotation coppice and miscanthus crops) were also excluded from the analyses.

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Question 2 : What geographic resolution is available for the study results? How accurate are the results?

The results have been published at the scale of the administrative region.

More generally, the published results are considered to be statistically acceptable. To reach this level of accuracy, a threshold surface area (or length for hedgerows) was defined as follows: 36,000 ha for forests, 20,000 ha for poplar plantations, 20,000 km for hedgerows, 1,500 ha for vineyards and 1,000 ha for orchards. Threshold values for forests, poplar plantations and hedgerows were based directly on IFN standards for statistical accuracy.

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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Question 3 : How are the ADEME and MAAP 2009 biomass studies linked?

Two studies on available woody biomass resources for energy production were carried out in 2008-2009, one for the ADEME (this study) and one for the MAAP.
The two teams collaborated on the study of forest resources. In order to ensure coherent published results, data, methods and hypotheses were shared or commonly defined. Both studies started with the same data for global forest resource availability and one of the scenarios proposed in the MAAP study is based on that data. However, the results expressed in net availability reflect different objectives. The two studies are therefore complementary. Where the MAAP study defines accessibility in technical terms (slope, etc.), the ADEME study includes both technical and economic considerations.

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Question 4 : What types of wood are potential sources of energy according to the study?

Potential uses of a woody resource can be defined in dimensional terms (diameter, length). However, large diameter size does not necessarily mean that the wood is good enough for high-end uses (joinery, peeling, construction timbers). Wood quality criteria must be taken into account along with dimension when defining potential uses of the resource.

In our study, we assumed that potential construction-wood-quality (CW) resources will always be used for construction wood. We also assumed that the price of fuelwood would never be higher than the price of construction wood and that potential resources of woody biomass for energy production (industrial roundwood and woody biofuel) could not be used as construction wood. In addition, the respective volume of construction quality wood (CW) and industrial roundwood and woody biofuels (IRWB) in a tree was set for each species and each region by local and national experts.

Sawmill by-products and waste wood have been excluded from the study.

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Question 5 : Can the study results provide enough information to define an energy supply plan for an industrial site?

No, the available wood supply for a given heating plant, for example, cannot be directly inferred from the results. However, the general regional estimates provided by the study coupled with a detailed analysis of locally available technical and economic data could provide a basis for an energy supply plan.

Our study provides information at the national scale in response to a specific request by the French government and therefore does not include regional specificities.

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Question 6 : Were the consequences of the Klaus wind storm (24 January, 2009) taken into account for the Aquitaine region?

Yes, the consequences of the storm have been partially taken into account.

Standing volume remaining after the storm was included (by applying damage rates to the pre-storm standing volume) to which we applied the sustainable forest management scenario. Available volumes of green wood were calculated for CW, IRWB and SBW, as for the rest of the study.
However, estimates for IRWB volume from windfalls were not made due to a lack of trustworthy data on the amount of wood being salvaged at the time of the study. Therefore, volumes of IRWB in Aquitaine are certainly under-estimated.


Damage to poplar plantations was also not considered. In any case, IFN estimates show that the level of damage was relatively low in these areas.

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Question 7 : Were recent objectives to increase harvest volumes taken into account in the economic evaluation?

No, global wood availabilty was calculated using a purely silvicultural and technical approach; in other words, harvest volumes were based only on sustainable management principles. The model shows wood supply and does not test the consequences of a possible change in demand over the period considered.
Any government incentives that may be put in place, for example subsidies for cable logging in mountainous regions, would assumably modify the market price and allow new resources to become economically viable.

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Question 8 : How were woody resources in protected areas calculated?

The harvesting restrictions applied to protected areas were not taken into account due to a lack of consolidated national information on the type of constraints that exist in these areas.
However, it should be remembered that forested areas whose primary or secondary function is not wood production have been excluded from the IFN analyses. These areas partially overlap certain protected sites.

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Question 9 : Harvesting of private forest resources may be limited by fragmentation and a reticence to sell on the part of some land owners. Were these factors taken into account?

No, ownership patterns for private forests and willingness on the part of the owners to put wood up for sale were excluded from the study. Current knowledge and data are insufficient to model forest-owner behavior patterns at a national scale.

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Question 10 : Was road access taken into account in the evaluation of available resources?

No, ease of harvesting was determined by directly observing the stand and its immediate environment. Information about local access roads is not always available, and even when it is, it may not be adapted to use in a national study.

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Question 11 : Were social and environmental criteria included in the evaluation of available fuelwood resources in hedgerow regions?

Hedges play several roles (economic, social and environmental), as does the forest. Our estimates of available hedgerow biomass exclude any parameters related to owner objectives or management choices, because of a lack of consolidated socio-economic data at the national scale. We also excluded this aspect from our calculations for forests.

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Question 12 : How were prices calculated for standing wood and wood decked at roadside?

Standing wood prices fluctuate considerably depending on market conditions. We assumed that the owner (or manager) would not sell below a certain price, which could be assimilated to the base-line price at public auctions. To establish our minimum price, we retained the lowest selling prices for standing timber for each species and diameter class recorded in the ONF sales price lists since 1989. We assumed that this price came close to the minimum price accepted by the owner.

For wood decked at roadside, we referred to the final value for forest wood products between 1991 and 2007 (MAAP survey) for CW in several species and for IRWB. The highest value attained over the period can be seen as the best price the market could offer for forest products. Such favourable economic conditions are likely to correspond to high sales volumes for each product category. We used this maximum value as a reference. No distinction in pricing was made among regions, due to lack of available information.

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Question 13 : The price of wood delivered to the site (factory or heating plant) is crucial for industrialists. Has this price been estimated?

For the industrialist, the price of wood delivered to the site is the base-line reference, since production costs depend on it. For example, wood decked at roadside in a parcel nearby could be bought at a higher price than wood from a distant parcel. The notion of cost-effective harvesting on a parcel differs depending on the distance from the industrial site. When establishing any industrial energy supply plan, transport distance must be included in the cost calculations.

In the study, taking transport distance into account is difficult for several reasons:
1. Industrial sites and heating plants are definied by their individual capacity and geographic location. Each site has different average transportation costs. Our study does not focus on any one site. Therefore, setting either a reference distance or an average distance would be unreasonable;
2. The regional scale at which our results are presented is often larger than the supply area which would correspond to sites planned to date;
3. There are no statistics available on prices for wood delivered to the site. However, statistics do exist for wood decked at roadside, even if their reliability may sometimes be questioned.

In relation to our study, it is acceptable to hypothesise that industrial sites would be evenly distributed throughout the national territory. In this case, the prices for wood decked at roadside balance out, allowing us to retain as reference values the market prices for wood decked at roadside as listed in the survey on final values for forest wood products.

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Question 14 : Was the sensitivity of the economic model tested at the forest management scale in some areas?

The sensitivity of the model to variations in the main hypotheses was tested at the national scale. The approach chosen to respond to the request from the ADEME did not allow us to test the model on particular forested areas. A site-specific supply plan is necessary to take local constraints into account.

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Question 15 : Some current silvicultural operations result in lost woody resources (pre-commercial thinnings, clearing coppice from stands). How was this type of woody biomass included in the study?

Woody biomass lost in non commercial operations has not been taken into account; the waste wood remains on site and is considered unharvestable. However, if demand and prices increase sufficiently, these volumes, currently excluded from our study, could become harvestable.

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Question 16 : Does using grape vine wood as a source of energy cause any special problems?

Grape vine wood contains large amounts of silica. Unfortunately, no studies exist to date on the effects of burning grape vine wood in heaters. However, the quantity of scoria can be reduced by varying the type of wood used to supply the heating plant.

Care must also be taken to avoid potential health risks related to burning grape vine wood, particularly stems, which have often been treated with chemical pesticides. Due to a lack of available research, it remains difficult to assess the actual risks related to the possible presence of toxic substances in the smoke (heavy metals), or to inhaling dust during chipping and manipulation.

Using grape vines as fuelwood should be restricted to medium- or high-power heating installations which are equipped with efficient smoke filters.

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Question 17 : How can I obtain detailed results for a given region?

A tool is directly accessible through this Website that allows you to consult specific results. A data base of pre-calculated results for forest resources, poplar plantations and hedgerow areas is accessible. You can download user instructions by clicking on "Archives and Downloads".

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Question 18 : Is the Internet site for the previous study (www.boisenergie.ifn.fr) still accessible?

The current study has updated and improved the previous study (2005). However, the Internet site for the 2005 study is still accessible by clicking on "Archives and Downloads".

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Question 19 : How can I download the final report and the summary?

The final report, a summary of this study, the report from the MAAP study, etc. can be downloaded by clicking on "Archives and Downloads".

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Question 20 : Where can we find the conversion factors used in the study?

The conversion factors used in the study can be found under "Glossary and Coefficients", then "Conversion Coefficients".

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