There seems to be limited research on geological exploration and mining of Guano islands or caverns within the cratons of Africa. The reasons remain unknown, probably it is due to the fact that they are not of economic interest, or it might be the fear of contracting cave disease and inaccessibility.
By Nomsa Ngono
This article seeks to dive deeper into both geological exploration and mining of bat guano.
Geological exploration was conducted on various Guano mining caverns surrounding Zimbabwe. Some of these were Mabura Caverns, which stretch for more than 60 km from Zhombe East to the Copper Queen area in Gokwe, passing underneath the Ngondoma River.[1] Another deposit was Bashungwi in Hurungwe, located in Magweto Village, which has massive deposits with a 15-20 year life span. More listings on discovery were Chingwena deposits in Kadoma, Mburangwe deposits in Makonde and Odzi Deposits in Mutare.[2]
Bat Guano
Bat Guano produces phosphorus, which is used to manufacture fertiliser. The major source of phosphate used for fertiliser production is mined from Mesozoic deposits at Dorowa Minerals.[3] There is a lack of competition and alternatives to the production of phosphates, which compromises fertiliser production prices, which are always prone to abuse. The article will further explore the genesis of the Anthropocene, a revolution between soil phosphorus and human productivity. This will be done through assessing the enormous impact of hydrocarbons from rock phosphates on climate change, which might necessitate geoscientists to consider Guano Mining either as an alternative or a competitor in minerals mined for agriculture.
The geological exploration of phosphate resources was carried out by the Geological Survey of Zimbabwe in 1991. The geological exploration conducted was for both rock carbonatite deposits and bat guano deposits from various caverns. Rocks associated with carbonites and cave accumulation of bat guano are the only two potential commercial occurrences of phosphates in Zimbabwe.[4] However, major attention and highlights shall be on bat guano phosphates. Mineral deposits of bat guano formed over a million years ago by the accumulation of excreta and bat remains. This occurred within caverns in Precambrian Proterozoic dolomarbles of the greenstone assigned to the Mucheka formation of the Lomagundi group. [5]In almost every instance, the caverns occur in limestone formations dissolved by acidic rain. Bat phosphate then composes in dump caves where bacterial action would have taken place, and possibly the deposit would have been subjected to leaching, leading to the formation of phosphorus.
Though studies were carried out on the geology of bat caverns, the Ministry of Mines and Mining Development has not reached a point of considering bat guano as a mineral under the Mines and Minerals Act. Therefore, Guano Mines cannot be pegged under a prospecting license as the title of ownership is restored with the landowner.[6]Almost all guano mines in Zimbabwe are under the jurisdiction of the respective Rural District Councils. The question remains: how do we then classify guano? As mineral deposits or agricultural chemicals? Nevertheless, since 1800 to date, other countries across the globe have considered guano as a mineral deposit. Guano mining and guano trade contributed to industrialisation and urbanisation in parts of Europe and Latin America. Zimbabwe’s lack of participation in guano mining hinders the global mineral resource supply chain. A considerable review of the Mines and Minerals Act to declare guano as an Agricultural mineral resource is worth a milestone in revitalising both agriculture and mining, which are the springboard of the Zimbabwean economy. The benefit of the project is for the poverty-stricken communities lying within the vicinity of the guano caverns. Guano mining projects usher in elements of employment creation, industrialisation and urbanisation within the respective Rural District Councils.
Like any other mining activity, mining guano is labour-intensive. Historically, companies relied on slavery, indentured servants, prisoners and migrant labour.[7]Mining was highly manual, using picks, brooms and shovels to loosen guano. The use of excavators was and is still prohibited because it is not only impractical due to the terrain, but it could frighten and disturb birdlife in the caverns. Caverns are often altered by explosives and drilling to facilitate guano extraction. The unabridged extraction process alters the microclimate within the caverns. Of great importance when mining guano is considering bats’ sensitivity to microclimate, which may prompt bats to abandon the caves as roosts. Like any other mining shaft, caverns are dark hence, mining procedures may introduce artificial light into the caves.[8] Considering the methods used in the process of extracting bat guano, mainly explosives and drilling machines, guano is indeed an agricultural mineral deposit of great value, worth classifying under the Mines and Minerals Act. The Ministry of Mines and Mining Development is compelled to assess the viability, feasibility and sustainability of Guano Mining projects in different parts of Zimbabwe and whether they are able to sustain the fertiliser industry in the long run.
However, Guano as a raw material is a poorly balanced manure which needs the support of other chemicals or substances to manufacture a suitable fertiliser. For example, the addition of sulphate potash to guano phosphates could make a great fertiliser. Nitrogenous guano with wood ashes proves a suitable fertiliser for maize and tobacco. Bat Guano in many caverns around Zimbabwe is of considerable value when made up of an approved formula with approved ingredients. More so, into the bargain, if guano phosphate fertiliser is sold at a cheaper price than imported or other fertilisers it could be in great demand. [9]Henceforth, the revival of guano mining in Zimbabwe under the wings of the Ministry of Mines and Mining Development could yield great economic prospects by introducing a new variant which will go a long way in expanding fertiliser-producing companies which heavily depend on phosphorus resources derived from the rocks.
As much as two-thirds of the world’s known phosphate resources are composed of carbonate-rich phosphate rock; exploitation of phosphate deposits provides a potential contamination of the ozone layer, areas surrounding the mines and areas where phosphates are used by increasing heavy metal levels.[10] Rock phosphates contain heavy and radioactive elements considered to be toxic to both humans and animals. The carbonates and phosphates have been identified as potential pollutant host minerals. High-grade quality rock phosphate deposits are being depleted worldwide due to increased agricultural activities, so more and more mining companies are turning to lower-quality sources of phosphates.[11] These lower-quality phosphates could be attained from bat guano phosphates. Considering the life span of Dorowa Mine, which is 60 years of marginal exploitation since its establishment in 1965, the phosphate resource is on the verge of depleting; therefore, there is a need for supplementary sources of phosphates from bat guano to sustain the fertiliser industry and boost international agricultural trade and domestic consumption.
Whilst deliberating on climate change, Agricultural scientists are mulling a shift to green farming by reducing the impact of hydrocarbons on planet Earth. Geologists on the other hand, are pestering on a green revolution between soil phosphorus and human productivity, termed as Anthropocene. Their main objective is to replace the nutrients extracted from the soil by crops. Humans have added all sorts of nutrients to the soil with hopes of enriching it, somehow to no avail. Although the list of traditional fertilisers is exhausting and bizarre, none has a strong history as guano, which was once the agricultural equivalent of gold, best described as the “white gold of agriculture.” Historically, the marketing of Guano in Zimbabwe was controlled by the Fertiliser Act of 1932 and the Farm Feeds and Remedies Amendment Act of 1976. This states that no fertiliser shall be sold under the name or description of Bat Guano. Under such conditions, fertiliser shall contain 2.5% of nitrogen or 8% nitrogen and phosphorus taken together, and much of guano does not meet this criterion[12] On the contrary, the stated criterion can be met when bat guano is mixed with other organic compounds or ingredients to come up with a proper formula for fertilisers.
Finally, until the danger of cave disease is fully assessed, geological exploration of the caverns should be carried out by men who either have a positive Histoplasma skin test or have previously explored the caverns with impunity, because one attack of cave disease gives immunity to further attacks.[13] Other than that, explorers, geologists and miners are required to wear fully geared PPE along with respirators and oxygen supply to be able to contain chemicals that affect the chest. Thereafter, the Ministry of Mines and Mining Development will be in a position to consider declaring bat guano as mineral deposits under the Mines and Minerals Act. Back in 1800 Guano mining industry proved lucrative, it was a catalyst for industrialisation and urbanisation in parts of Europe and Latin America. With the 21st-century geoscientists advocating for green revolutions in the agricultural sector, a boom and bust of Guano Mining is optimistic. Shifting to organic energy is the only way to save planet Earth. A reduced use of carbonate phosphates from rocks reduces land degradation and mitigates the destruction of biodiversity, and water, land and air pollution. Organic energy, therefore, reduces the cost of climate change mitigation in line with the Paris Agreement. However, a lack of research and compliance by some key mining fraternities and responsible ministries hinders Zimbabwe’s participation in the global mineral resources-based supply chains. It only takes enough investment in guano mining to sustain meaningful levels of economic growth.
Nomsa Ngono is a Phd History candidate studying with the University of Zambia. She is a holder of a Master of Arts in African History degree, a Bachelor of Arts in International Studies, ISO 9001 Quality Management System internal audit certificate. Her research interests are mining, peace, national healing and reconciliation, exhumations and reburials.
You can get in touch with Nomsa on: [email protected]
[2] Flack.E.V, “Bat Guano Deposits of Rhodesia,” Sabinet African Journals,1920
[3] I.kwesu etal,” Mining Sector Policy Study,” ZEPARU,2012
[4] B.Barber, Phosphate Resources of Carbonites in Zimbabwe, Kluwer Academic Publishers, Netherlands,1991,p 19
[5] Ibid
[6] B.Barber, Phosphate Resources of Carbonites in Zimbabwe, Kluwer Academic Publishers, Netherlands,1991,p
[7] B.Boyce, The Guano Trade,2022
[8] Guano, Encyclopedia, Science News and Research Reviews.
[9] Flack.E.V, “Bat Guano Deposits of Rhodesia,” Sabinet African Journals,1920
[10] Meck.M.L etal, ‘Minerals that Host Metals at Dorowa Rock Phosphate Mine Zimbabwe,’ The Open Mineralogy Journal, Volume 5 ,2011
[11] ibid
[12] B.Barber, Phosphate Resources of Carbonites in Zimbabwe, Kluwer Academic Publishers, Netherlands,1991,p23
[13] G.Dean, “Cave Disease,” The Central African Journal of Medicine, Volume 3, Number 2, March 1957,p81
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