The 1988 Directive set progressively declining emission ceilings for existing power stations and other large boilers in each Member State. By 2003, total sulphur dioxide emissions from these sources are required to fall by 57% from the 1980 level, while emissions of nitrogen oxides must fall by 30% between 1980 and 1998. The Directive also set limits on emissions of SO2, NOx and particulates from new plant.
An initial proposal to revise the Directive was circulated by the Commission last year (ENDS Report 255, pp 42-43 ). This proposed further cuts in emissions by 2005 and 2010 from a new 1990 baseline, arousing complaints from some of the greener Member States that they were being penalised for taking early steps to reduce acid gas emissions.
However, the controversy over the initial proposal pales beside that provoked by the latest draft, which the Commission presented to Member States and industry representatives at a meeting in Brussels in May:
The proposed ceiling on the UK's SO2 emissions is 15 times tighter than in the earlier draft. The new proposal would also require much deeper cuts in NOx emissions from the UK's combustion plant - all the more so because emissions from gas-fired power stations have now been brought within the scope of the proposal.
The dramatic lowering of the emission ceilings flows from the Commission's recently proposed acidification strategy (ENDS Report 266, pp 40-41 ). This would set each Member State emission ceilings for SO2, NOx and ammonia. Large combustion plant would be granted a relatively small allocation of the total, on the basis of cost optimisation studies carried out for the Commission by the International Institute for Applied Systems Analysis (IIASA).
According to IIASA's models, releases of SO2 from large combustion plant across the EC are set to fall to around two million tonnes per year under current commitments, including the 1994 UN Economic Commission for Europe protocol on sulphur emissions. The new draft Directive would therefore require a further halving of the sector's emissions.
Officials from almost all Member States reacted with hostility to the new draft Directive - with one describing the emission ceilings as "not feasible". France fears that the limits would restrict its plans to diversify from nuclear power. Sweden, the Netherlands, Greece and Spain questioned the need for sectoral emission ceilings within the national limits set by the acidification strategy - a position the UK is also expected to adopt once the new Labour Government has considered the proposals.
The emission cuts would be a further blow to the UK coal industry - providing an early test of Labour's environmental credentials. The Department of the Environment (DoE) points out that around half of the 2010 ceiling for SO2 would be taken up by emissions from Drax and Ratcliffe power stations, which are already fitted with flue gas desulphurisation equipment. Very little headroom would remain for refineries, other industrial sources or other power stations - even allowing for further FGD retrofits. The DoE will discuss the impact of the proposals at a meeting with industry representatives in June.
The hostile reaction to the Commission's proposals is likely to spell trouble for the wider acidification strategy. Indeed, Rob Ebbins, Head of Policy Coordination (Air) at the Scottish Environment Protection Agency, told a conference in May that the emission cuts under both the large combustion plant proposal and the strategy "look unrealistic, certainly by 2010."
The Commission sought to calm Member States by stressing that the emission reductions proposed under the acidification strategy, and therefore the revised large combustion plant Directive, remain provisional until agreement is reached on parallel emission cuts to reduce low-level ozone pollution.
The impact of the proposals may be rather less drastic than Member States fear, as IIASA's models for 2010 fail to take account of reductions in energy production which are likely to be needed to meet future commitments on climate change. The Commission has asked Member States to provide better data on current and projected generating capacity, plant size and fuel usage before the next meeting in July in order to check the accuracy of IIASA's models.
The standards for new solid and liquid fuel-fired installations have remained broadly unchanged from the initial draft. Lower limits have been set for SO2 and dust from smaller installations with a thermal capacity of 50-100MW, bringing the proposal closer into line with Environment Agency guidance (ENDS Report 251, pp 28-29 ).
However, the Commission's proposed emission limits for gas turbines were criticised by many Member States as too tight. NOx emissions from gas-fired turbines - including gasification processes such as "clean coal" power stations - would have to be below 20mg/m3 for plants which are less than 35% efficient (see below). The Commission has set up a working group to assess whether the limit is achievable.
The Commission has now dropped all reference to minimum efficiency standards. Instead, the draft says, new installations "shall be designed and operated in order to achieve a high energy efficiency."
The revised proposal offers two boosts to CHP. Firstly, cogeneration of heat and electricity would be expected of new plant unless the operator could justify to the licensing authority that it was not technically and economically possible. Secondly, a "bonus" system would mean that less stringent NOx emission limits would apply to gas turbines with an efficiency greater than 35%.
Several other issues remain to be settled. The question of how to deal with aggregations of small and medium-sized combustion plants on a single site - already an area of some disagreement between Member States - is likely to be made more pressing by the tough emission ceilings. And the relationship of the large combustion plant proposal to the 1996 Directive on integrated pollution prevention and control (IPPC) has yet to be agreed. At present, the Commission maintains that the proposal is not a daughter of the IPPC Directive - and that the cost constraints implicit in the latter's definition of "best available techniques" do not apply.