An assessment of ways to abate ammonia emissions from livestock buildings and waste stores. 2. Cost modelling

The economic consequences of different ammonia abatement approaches, used either singly or in combination, have been examined by means of a specially developed mathematical model called Sectoral Analysis of Livestock Ammonia Abatement Model (SALAAM). SALAAM basically uses a "process-based" approach, characterising livestock waste management as a cascading system in which flows of Total Ammoniacal or Available Nitrogen (TAN) through different types of system, and through different stages of waste management (e.g. housing, storage, application to land), are linked into an overall flow network. This allows individual calculation of ammonia emissions from different parts of the waste management process, and systematic analysis of the effects of changes in the system (e.g. through implementation of abatement measures) by adjusting flow volumes within each pathway. The model was used to carry out three separate exercises: (a) to determine the economic value of individual abatement measures, (b) to calculate maximum feasible reductions, and (c) to estimate potential abatements in relation to the sector livestock values. The results from SALAAM were as follows. For (a), the ranked unit cost (lbs/kg NH(3) abated) followed an exponential curve, the overall range of unit cost, in the above units, being from zero to many hundreds. The approaches of dietary manipulation, individual feeding, industrial scale processing, fixing with acid and animal breeding showed up well, with low unit costs in each of several sectors. For (b), the maximum feasible reduction was rather lower for the cattle industry (at just over 40%) than for the pig and poultry industries (at around 70%). For (c) the potential emission reductions at an expenditure level of 10% of the annual value per animal place were calculated. With pigs and poultry, abatements close to the maximum feasible reduction were achievable at an expenditure of not more than 10% of the annual value, but with cattle, especially non-dairy, much higher percentages of the annual value would need to be expended to approach the maximum feasible reduction. There was general agreement between the results from these modelling techniques and those from a complementary ranking technique, but no one single approach is likely to solve all building and store abatement problems. Rather, it will be necessary to deploy, on a national scale, a combination of approaches, each of which has been carefully selected from amongst those identified as promising during this study. The results, both of this modelling work and of the complementary ranking exercise, reported in a companion paper, would be made more robust if stronger and more complete cost data than those which have so far been available could be sought out and/or estimated for the various different abatement approaches identified.