Technical
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Phosphogypsum, and associated contaminants may be a ‘necessary evil’ of the phosphate rock industry, but are they an ‘unnecessary evil’ in the wider context?
It is with a degree of concern that I write of the above, and even moreso when I highlight the fact that, whilst Piney Point is an extreme case, it is not an isolated one. There are many more such stories from plants in Florida, Mississippi, Spain and further afield. Whilst I appreciate that regulatory bodies are implementing further control measures, I would have to point to the basic fundamental principles of risk management - the first, and most successful of which is to remove the risk. Phosphogypsum, and associated
contaminants may be a ‘necessary evil’ of the phosphate rock industry, but are they an ‘unnecessary evil’ in the wider context? My personal belief is that we are working with an ageing technology and, with this, comes a natural suppression of further research and discovery of alternative phosphorus sources. I would implore the fertiliser industry to question the current methods of phosphorus production, ask that they weigh the benefits of their business against the environmental impacts that it creates, and ultimately, seek alternative means of providing useable products that come without such environmental burdens. Eutrophication - Another significant
I will stick my neck out and argue this point - phosphorus is mobile in soil, and does leach, particularly where excess levels above plant requirements are found
134 I PC APRIL/MAY 2015 ”
environmental threat is that of eutrophication - this ecological response is fuelled by nutrient enrichment of inland and coastal waterways. Increased algal biomass is the net result of this nutrient enrichment, and leads to anoxic conditions, thereby leading to the death of several marine species, including important fish and invertebrate stocks. Furthermore, algal blooms and invasive marine plant species become rife, and reductions in species biodiversity are commonly referred to. Phosphorus and nitrogen are the two main
contributory factors to this condition; however, for the purposes of this article, I will solely focus on the contribution of phosphorus. I am sure that many of you will have seen images of algal blooms in waterways - they are not an uncommon sight, but I ask, how many stop and think of the cause? How many stop and consider what we contribute to this issue? As nutrient enrichment is the prime driver of
this ecosystem response, I would suggest that Liebig’s Law of Minimum takes centre stage here. Phosphorus is widely acknowledged as the primary limiting factor for eutrophocation - put simply, if we limit the amount of phosphate which finds its way to our inland and coastal waters, we limit eutrophication. The two main vectors for phosphorus
movement into waterways are run off and leaching. There are several mechanisms that can be employed to reduce surface run off - the most successful of which is to simply ensure adequate levels of ground cover. Leaching is another, perhaps more significant issue where our industry is concerned - most will happily state that phosphate is immobile in soils - I will stick my neck out and argue this point - phosphorus is mobile in soil, and does leach, particularly where excess levels above plant requirements are found. With high specification drainage schemes
commonplace in many a venue now, along with high levels of phosphorus fertilisation, many of us are unwittingly contributing to the point source of phosphates entering our waterways - it is time that our industry acknowledged this fact, and I will add in that this should be the case for all known environmental pollutants, as I state that alternative products, and alternative methods are key points for our industry to reduce its environmental burden. To summarise my feelings from the points
raised in this, the second in this series of articles, I think it is clear, from the passage of the information contained in this article, that the phosphate rock processing industry is not without issue. It is a fact that overuse of phosphate fertilisers suppresses the soils natural phosphorus acquisition mechanisms, and it may come as a surprise to many to note that this rule applies to organic sources as well as mineral - quantity is the driver of biological shutdown, not source material. With that said, the additional contaminants
contained within mineral sources can accumulate in soils and lead to plant and biological phytotoxicity, as per the rules of the Law of Tolerance. Purely from an agronomic perspective, it is my belief that first and foremost, it is incumbent upon us to protect the natural processes of the soils which we work - the way that this is achieved is twofold. Firstly, there is a fundamental lack of
reference to suitable and sufficient complex carbon sources in this industry - complex carbon sources are vital to ensuring that microbial biota have the foundation to proliferate from. Secondly, the overuse of a number of products simply must come to an end. I have demonstrated the effects of ‘enrichment’ of watercourses in the section regarding eutrophication - it is my belief that the negative effects of this enrichment are not limited to waterways, and I believe that soils
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