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L’énergie dans le développement de la Nouvelle-Calédonie

 | 
Yves Le Bars
, 
Elsa Faugère
, 
Philippe Menanteau
, 
et al.

Emissions and the reduction of greenhouse gas emissions in New Caledonia

The potential use of imported lignocellulosic biomass and products locally as a substitute for coal in nickel production

Texte intégral

1What options are there to reduce greenhouse gas emissions by replacing coal with other sources of energy, and lignocellulosic biomass in particular? The vast majority of any lignocellulosic biomass would undoubtedly have to be imported, with some small reliance on local production; this proportion could possibly increase if development of the land in New Caledonia permits.

2The timber industry currently generates its electricity from timber plus there are also, in the United States in particular, numerous wood-fired electricity generation stations where output generally hits a ceiling of 49 MW. There are also some in Europe: for example, the electricity generating station in the city of Liège, which previously operated on pulverised coal, now uses wood pellets which are imported by ship. In Copenhagen, straw pellets are being used in place of coal, and the Netherlands is also conducting serious study into the possibility of importing wood to improve its greenhouse gas balance sheet. There are plans to install a large heat generating plant at the port of Rotterdam. In Poland, coal-fired electricity generating plants have invested to replace at least 20 % of their coal with wood since CO2 emissions exceeded €20 per tonne.

NICKEL: A HIGHLY COAL-INTENSIVE INDUSTRY

3The best method of producing nickel emits almost as many greenhouse gases per tonne as production of a tonne of aluminium which in turn emits ten times more greenhouse gases than average production of one tonne of steel. With two new units commissioned, emissions are set to rise further. It is thus important to find ways of reducing these emissions, in particular by adopting more efficient industrial processes. We could imagine for example, when the time is right, replacing old factories with new, more efficient factories. However, the new investment that would be needed can be considered only when the old installations have become obsolete, or if the penalty per tonne of CO2 emitted were to increase to a point where the planned replacement of old installations would become worthwhile.

4Over the course of the next decade, it will be possible to reduce green-house gas emissions by changing the fuels used. At some later stage, possibly after 2020, it may also be possible to link biomass use to geological storage of CO2. CO2 emissions from coal would then drop to zero, and emissions from biomass would be negative. However, there would no doubt need to be insistence on achieving the initial stage independently of the feasibility of geological storage.

THE APPEAL OF LIGNOCELLULOSIC BIOMASS IN RELATION TO COAL IN ELECTRICITY GENERATING PLANTS AND METAL FACTORIES

5Carbon dioxide emissions per tep of primary energy vary according to the fuel used: given the same heat output, coal emits 40 % more CO2 than oil, and 87 % more than natural gas. All things being equal, heat generated from lignocellulosic waste, renewed lignocellulosic products (wood, plants, etc.), natural gas, or oil, is far better than heat generated from coal. Replacing coal with renewed lignocellulosic biomass throughout the industrial process would enable emissions to be cut by around 4.5 teqCO2 per tep. The production of one tonne of nickel currently requires between 4.5 tep and 6 tep of coal.

6Depending on the primary energy source used to produce electricity - lignite, coal, fuel oil, natural gas, biomass, uranium, wind or hydraulic power plants - emissions may vary from 400 g to 1 kg of CO2 per kWhe (a full table of CO2 emissions by primary energy source used is included on the CD ROM).

7Biomass emissions per kWh of electricity produced reach only 4.4 % of the emissions from coal (46 g of CO2 as against 1 022 g of CO2). Electricity generation, with gasification in a combined cycle based on coal or biomass is also better for the climate if renewed biomass is used because this latter is virtually neutral in climate terms, and purifying the flue gases from a coalfired power station requires more energy than the flue gases emitted by biomass. Using 5 % or 15 % biomass can reduce the greenhouse gas emissions from a coal-fired power station by 6.7 % and 22.4 % per kWh of electricity generated respectively.

8Co-combustion of coal with biomass is already happening in several locations: in the Netherlands, 250 MW coal-fired power stations use (to cover around a tenth of output) wood chips and pulverised chicken excrement; on the islands of La Réunion and Mauritius, coal is being used to supplement bagasse in the periods when bagasse is not available.

9Finland’s large municipal power plants, in the city of Jyvääksla for example, cogenerate heat and electricity using wood and peat.

10Arcelor (now Arcelor Mittal) in 2000 launched a research programme (Ulcos, Ultra Low CO2 steel) to replace mineral coal by wood coal in the manufacture of pig-iron, as in Brazil. However, increased carbonisation of wood is currently justifiable only in the production of high quality steel.

THE TECHNICAL FEASIBILITY OF USING BOTH COAL AND DRY LIGNOCELLULOSIC BIOMASS

11Co-combustion of wood and coal in large heat generation plants in theory remains the most economic solution, but is not the most efficient solution in energy terms. If yields are to be optimised, it would be better in theory to burn solid fuels in different power plants and centralise heat production.

Where does this lignocellulosic biomass originate from?

  • 1 In Brazil, average growth per ha and per annum can reach up to 40 t de MAS in the state of San Pau (...)

12It may come from renewable lignocellulosic biomass (such as landfill) or may not yet have been harvested. More could also be extracted from New Caledonia under certain circumstances (cf. “New energy production and storage technology”). It is estimated that eucalyptus tree production could pro-vide 10 to 12 tonnes of dry matter per hectare1, or around 4 tonnes of tep. If these trees were fertilised, it would no doubt be possible to produce, over one hectare, the energy needed to manufacture 1 tonne of nickel. For the 200 000 tonnes of nickel manufactured in 2007, around 200 000 ha of highly productive forest would therefore be needed (or 500 000 tonnes of dry matter, a little less than the requirements of a large pulp factory) to provide the energy needed to manufacture with very low emissions levels. In New Caledonia, however, even in the best case scenario, it would no doubt be possible to plant only a few hundred hectares of highly productive forest which could be worked mechanically. Making up the shortfall in need, which would rise when the two new units are commissioned, would therefore mean reliance on biomass imports while continuing to use coal.

13Like pulp factories, these production units could import wood by ship – logs, untreated wooden sheets (unstripped wood shavings), or even wood pellets or briquettes. New Zealand, Canada and Brazil could certainly pro-vide such products as required. In the tropics, there is a lack of awareness as to what to do with certain lignocellulosic biomass products. But here again, if the target is the global market, true feasibility depends on the cost of harvesting products and of transporting them to the factory or port (the economic cost and the energy cost of transport by ship are generally very low).

14Partial substitution of coal by biomass could therefore very quickly be of interest in New Caledonia, even if some of the biomass has to be imported. A feasibility study would be able to estimate the cost per tonne of CO2 prevented and the cost of wood above which such action would be beneficial. Consideration also needs to given now to the possibility of establishing storage areas, and biomass transfer and packaging systems in the factories that would use it. To remain economically competitive, biomass must be handled as little as possible and it must be capable of being harvested mechanically.

15At a later stage, after 2020 undoubtedly, it should be possible to combine plant biomass energy production with geological storage. Here too, economic simulations could prove useful.

16Prefeasibility and feasibility studies could be co-funded by manufacturers, Enercal and the government of New Caledonia.

Notes

1 In Brazil, average growth per ha and per annum can reach up to 40 t de MAS in the state of San Paulo. Average production of 20 t of dry matter is the current norm provided the fertilisation and rainfalls patterns are sufficient.

© IRD Éditions, 2010

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