Development and implementation of air pollution mitigation systems for animal husbandry in The Netherlands
Being one of the most densely populated nations in Europe, and housing an economically important livestock industry, the Netherlands face the challenge to strictly control environmental impacts of livestock production on residential and natural areas. The aim of this paper is to describe the main characteristics of the approaches followed in this policy with the focus on ammonia emission mitigation. It outlines technological developments and the implementation of mitigation technology in practice, and discusses benefits and drawbacks of the followed approach, and the possibility to make use of developed mitigation options in other regions with different productions settings. Since 1980 the ammonia emission from agriculture has been reduced by nearly 50%. This major achievement can be attributed to a number of general measures related to mandatory manure storage covering, low emission manure application techniques, and the implementation of low emission housing systems. Low emission housing systems have been developed for all main animal categories. Low emission is generally reached by restricting emitting surfaces, and quick removal and drying of manure. In general ammonia emissions were reduced by 50% and more, when compared to existing conventional systems. Higher reduction levels (70-90%) can be reached by air scrubbers. All measures were tested on practical farms using standardized measurement protocols. Low emission housing systems developed in one region cannot be simply transferred to other production regions. However, most of the mitigation principles that underlie these housing systems can be successfully applied in other settings as well, if modified and adapted to local conditions.
Standardized testing procedures for assessing ammonia and odor emissions from animal housing systems in The Netherlands
The Green Label measurement protocol (GL protocol) was developed in the mid nineties to evaluate the ammonia emission of low emission housing systems and other mitigation measures in the Netherlands. The measurements are used to assign official emission factors to low emission housing systems, used in farm permit procedures. More recently a new multi-site sampling approach has been developed, based on the experiences with the GL protocol and results from a statistical analysis of an extensive ammonia emission database. The objective of this paper is to describe and explain the evolution process from the GL protocol to the multi-site approach. Key features of the GL protocol are: evaluation at one farm location, long measurements during winter and summer periods, continuous high frequency sampling, ranges to stay within for critical management factors. In 2005 a statistical analysis was performed on a large ammonia emission database of pig housing systems that provided estimates of so called between farm(s2b), within farm (s 2 w) and instrumental measurement variances that determine the accuracy with which the mean ammonia emission of a housing system can be measured. The analysis demonstrated that both s2b and s 2 w of housing systems varied in the range of 30 - 40% ( relative standard deviations). The large size of s2b implies that the accuracy of the GL protocol is strongly limited by its single farm approach. Recently a new multi-site sampling approach has been approved based on four farm locations where at each location six independent 24h sampling intervals are distributed over one year. The multi-site approach allows for a less intensive and less costly measuring effort for each location, whereas the accuracy of the mean yearly ammonia emission of a low emission housing system is drastically improved.
Addressing biofilter limitations: A two-phase partitioning bioreactor process for the treatment of benzene and toluene contaminated gas streams
A two-phase partitioning bioreactor (TPPB) achievedsimultaneous and continuous removal and degradation of benzene and toluene froman air stream. The aqueous-organic system utilized n-hexadecane as the organicphase, and the organism Alcaligenes xylosoxidans Y234 in the aqueous phaseto achieve the degradation of benzene and toluene. The system, which operates asa well-mixed dispersion and is therefore resistant to substrate surges, was firstshown to be capable of utilizing toluene while operating at a loading capacity of 235 g m-3 h-1with an elimination capacity of 233 g m-3 h-1. It was also determined that to characterize TPPB performance in terms of elimination capacity thedefinition of elimination capacity must be extended to include the cell mass present, a readilycontrollable variable given the nature of the system. Based on this criterion, it wasestimated that for a cell concentration of 1 g l-1 present in the TPPB, thepotential maximum toluene elimination capacity is 1290 g m-3 h-1 whichis substantially higher than any toluene elimination capacity achieved by biofiltersat a high removal efficiency. If no other factor were to limit the system, eliminationcapacities could be many times higher still, and are dependent on maintaining desiredcell concentrations above 1 g l-1. The TPPB was then operated at nominalloading capacities of 63 g m-3h-1 (benzene) and 51 g m-3 h-1 (toluene) at a removal efficiency greater than 99% to demonstratedthe applicability of this system in dealing with two chemical species simultaneously. TPPBsystems therefore have been shown to be effective at removing gaseous organiccontaminants at high removal efficiencies while also possessing desirable operatingfeatures, such as providing and maintaining high cell concentrations throughout thereactor, and a capacity to effectively deal with high contaminant loadings.