Restoring Soils in Kilimanjaro – Engineers Without Borders Seeks Funding to Fight Food Insecurity in Tanzania

  • Mount Kilimanjaro

This project contributes to Sustainable Development Goals


David Paul Blessing examines volcanic rocks that will be used to produce a locally sourced, nature-based fertilizer for small-scale farmers in the Kilimanjaro region, Tanzania.

David Paul Blessing, President of Engineers Without Borders (EWB) in Tanzania, has a science-backed plan to bring better outcomes to small-scale farmers, their families and communities in the Kilimanjaro region in northeastern Tanzania.

Across Tanzania, agriculture employs 75% of the working population. Soils vary dramatically from region to region in their mineral and nutrient composition, affecting the soil’s fertility and farmers’ ability to grow nutritious food. In regions with naturally low soil nutrients, subsistence farming remains a challenging means of survival. 

Serious problems like low soil fertility, prolonged droughts driven by climate change, soil depletion from large-scale agriculture, and skyrocketing fertilizer prices (fueled by the Russia-Ukraine conflict, which has more than doubled the cost of fertilizers) make it critical to introduce locally-sourced, sustainable alternatives to expensive imported fertilizers. Today over 90% of chemical fertilizers used in Tanzania are imported, and an estimated 95% of small-scale farmers cannot afford them.

The challenge and a possible local solution

Farmers in the Milwaleni Springs community in the Kilimanjaro region, Tanzania. 

While it is possible to use synthetic chemical fertilizers to grow enough crops in low-nutrient soils to meet a community’s caloric needs, these fertilizers often lack essential micronutrients and minerals and thus do little to combat widespread malnutrition. The most common chemical fertilizers, based on nitrogen, phosphorus and potassium, are unaffordable and accelerate soil degradation. This results in soil acidification, loss of organic matter, reduction of beneficial soil organisms, and pollution of waterways. 

David Paul Blessing and EWB-Tanzania have identified a locally-sourced, nature-based alternative solution to promote the long-term health of soils in Miwaleni Springs in the Kilimanjaro region and the communities that rely on them. After noticing the wide disparity in soil fertility across the country corresponding to variation in geology, Blessing discovered the growing body of research on soil remineralization, the process of introducing finely ground rock powders to restore depleted soils. 

Remineralization produces several benefits that restore soils. It has been thoroughly studied and is now widely accepted as a viable, reliable nature-based solution. Remineralization formulations can be customized for the individual needs of each soil and are generally plentiful in the nutrients plants need, such as phosphorus and potassium, in addition to calcium, zinc, magnesium and other nutrients essential for human health. Remineralizing soils in Kilimanjaro can potentially increase crop yields and food nutrition, helping alleviate widespread poverty, food instability and malnutrition in the region.

Rented house in the Milaweni Springs community. This is the homebase for Rutubisha preparation, production (mixing, bagging) and initial testing.

Blessing is developing a locally-sourced agromineral-mixture to do exactly this.  Named Rutubisha — Swahili for “to apply nutrients” or “remineralize” — it includes rock powders sourced from a quarry on Mount Kilimanjaro. Each component of this blend has been well-studied and documented to improve soil nutrient availability, boost crop levels of micro and macronutrients, help soils retain moisture, and promote long-term supplies of necessary soil minerals. 

In addition to rock powder, Rutubisha will include local compost manure and biochar, a charcoal-like byproduct of agriculture and forestry that can sequester carbon for up to 2,000 years. Organic compost is already integral to farming across the region, and when paired with rock powders, it has been documented to expedite soil enrichment and help convert dissolving minerals into molecular and ionic forms that plant roots can absorb. The carbon sequestration potential of biochar will help offset emissions from mining and transporting the minerals used in Rutubisha.

Contribution of the project to the adoption of regenerative farming methods with long-term positive consequences.

Recent project successes

David Paul Blessing and Engineers Without Borders’ science-based approach, mastery of local logistics, and hard work have paid off with the successful production of an initial Rutubisha product batch in May 2023. Blessing’s concept of a locally sourced, nature-based fertilizer began over a year ago; however, no funding was available at the time. With the recent seed money provided by Remineralize the Earth, Blessing and EWB’s development of the Rutubisha product has been surprisingly rapid, given the limited funds and other challenges such as unexpected rainstorms.

In March 2023, Blessing and colleagues selected the Milaweni Springs community for the first phase of Rutubisha production, distribution, and testing on working farms. Also, in March, Blessing selected the Karamsingi Quarry as the Rutubisha rock source because of its high-quality basaltic rock and proximity to Milaweni Springs. After surveying more than five quarries, Karamsingi Quarry was selected due to:

  • Availability of high quality volcanic basalt which can be processed into a finely ground rock dust fertilizer,
  • Accessibility from a main road, only 300 meters,
  • Close proximity to the processing site, about 4 km,
  • Proximity to the community of Miwaleni Spring small scale farmers,
  • Availability of labor for collecting and loading the rock dust.
A simplified geologic map of the Kilimanjaro volcanic province showing the three main summits (Shira, Kibo and Mawenzi). Note the Rutubisha quarry is in the southern part of the Kilimanjaro volcanic province. Image credit: Sémhur, Wikimedia Commons.

The Rutubisha quarry is on the southern end of the Kilimanjaro volcanic province (see map), and is approximately 30 kilometers south of the Mawnzi summit. This region is dominated by solidified lava flows and lahars (volcanic mudflows or debris flows). The volcanic activity that formed the Kilimanjaro lava flows took place between 400,000 and 200,000 years ago. The rocks that formed from these ancient lava flows are particularly well suited for use as natural fertilizers because they are rich in essential plant nutrient elements such as calcium, magnesium, potassium and phosphorus and contain a wealth of beneficial trace elements.

In April of 2023, Blessing and EWB-Tanzania prepared an initial budget for Rutubisha production, which included collecting the Rutubisha raw materials, sizing the rock material (sieving), packaging the product, and distributing it. As part of this initial work, product labels were designed. 

EWB-Tanzania rented a house in Milaweni Springs to serve as the initial Rutubisha production facility, office space, and initial distribution center. Also in April, Remineralize the Earth provided seed funding for the project and began preparations to launch an IndieGogo campaign to further fund the initial phase of Rutubisha production/distribution and hopefully to provide for expansion of the project to surrounding regions. In parallel, EWB-Tanzania developed plans to work with local Tanzanian companies to sponsor Rutubisha production, so it can be provided to local farmers free of charge. 

Sieved product components of the agromineral mixture Rutubisha. The gray material is the volcanic rock dust, the brown is compost manure and the black is biochar.

The initial Rutubisha formulation was also established in April, after consultation with advisors at Remineralize the Earth. The first bagged lots of Rutubisha fertilizer will consist of 20 kilograms of basaltic rock dust (passed through 1-millimeter sieve), 2.5 kilograms of biochar, and 2.5 kilograms of compost manure. Initial test batches with this composition have been produced.

It is anticipated that, for future batches, material ratios will be altered to customize the fertilizer mixture to specific regional soil conditions. Formulations for Rutubisha-based animal and poultry feed have also been developed and are being packaged alongside the Rutubisha fertilizer.  

In May 2023, the first bags with the Rutubisha product labels (for 25-kilogram batches) were received and the first farmers to receive the first Rutubisha batches were selected. 

The plan

Rutubisha packaging

With just $8,000 and continued guidance by experts in remineralization, Blessing will provide a whole community with enough Rutubisha to achieve food security. Blessing is already beginning trials with farming communities near Miwaleni Springs in the Kilimanjaro region. With more funding, the team will collaborate with local farmers to incorporate Rutubisha into their existing farming techniques with manure compost and biochar, leverage local knowledge of the land, climate and ecosystem, and hone Rutubisha mixes for healthy soils, high crop yields and nutritious crops. Knowledge gained from this pilot in Kilimanjaro will be key to honing the best mixes and techniques for other regions across Tanzania.

Once it is fully funded, Project Kilimanjaro can drastically reduce poverty and open alternate employment opportunities when subsistence farmers begin producing and selling surplus crops. Another likely outcome is healthier communities due to reliable access to nutritious food and less poverty. Perhaps best of all, the community of Miwaleni Springs will no longer rely as heavily on imported chemical fertilizers and can sustain and expand on these developments for generations to come. 

To learn more about EWB-Tanzania and this project, visit EWB-Tanzania’s website, or contact Joanna Campe at

If you are an individual or impact investor and believe in the importance and potential of this project, please consider donating via our fundraiser Addressing Food Security in Tanzania.


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