The implications of food loss on East Africa's environment and water resources

Food loss and waste refer to the reduction in the quantity or quality of edible food that is intended for human consumption (Rezaei & Liu 2017). One-third of all food produced globally is estimated to be lost or wasted (Boliko 2019). This food loss is equivalent to 1.3 billion metric tons (mt) globally and is about 30–80% depending on the crop in Sub-Saharan Africa (Gustavsson et al. 2011a, 2011b; James & Zikankuba 2017). The bulk of the increase in agricultural output and consequent increase in food loss is predicted in South Asia and Sub-Saharan Africa, where agricultural production will need to double by 2050 (FAO 2017). In East Africa, where food insecurity is already prevalent (Bjornlund et al. 2022), food loss exacerbates the issue by reducing the availability of food resources for the population.

Food loss entails not only the loss of edible food but also the waste of valuable natural resources, including water, land, energy, and other resources that are required for food production (Bartali et al. 2022). The inefficient use of these resources results in a significant environmental footprint, which has negative impacts on ecosystems, biodiversity, and climate change. Water is a particularly critical resource for food production, and when food is lost, the water used to produce it is also lost. This wastage of water exacerbates the problem of water scarcity, which is already a significant issue in many regions, including East Africa. Despite overreliance on rain-fed agriculture, the repercussions of food loss are more severe in these agricultural-intensive regions undergoing episodes of climate change variability, represented by seasonal fluctuations in precipitation and temperature of varying severity and duration (Müller et al. 2011; Kogo et al. 2021). Understanding the magnitude of lost water resources provides an opportunity for potential water saving by reducing food losses and waste (Lundqvist et al. 2008).

Food loss varies significantly between countries, owing to differences in income, industrialization, and development. In developing countries, it is estimated that about two-thirds of food is lost at the post-harvest and processing levels (Chalak et al. 2016). Food loss in East Africa is very high, especially the perishable products, due to inefficient handling, poor transportation, and poor storage structures (Gustavsson et al. 2011a, 2011b). Naturally occurring pests (primarily insects) are also the leading cause of this deterioration, causing a substantial loss of yearly crop production. Precise quantitative assessment of losses has proven difficult due to the high variability in infestation from year to year (Costa 2015).

Consequently, the environmental impacts are so high regarding the amount of water wasted and the agricultural non-point pollution of rivers and carbon emissions. Opportunities such as improving agricultural water productivity and water-use efficiency have been identified to reduce water (Giordano et al. 2017).

Food loss and waste contribute to global food insecurity and significant economic and environmental consequences (Buzby & Hyman 2012). In an environmental sense, food loss and waste have many implications, including needless greenhouse gas emissions and inefficient water and land use, leading to diminished natural ecosystems and the services they provide (Lipinski et al. 2013). Three key related resources are freshwater, cropland, and fertilizers. Water is scarce in many regions (Kummu et al. 2012), and water scarcity is one of the vital challenges the human population faces. It is noted that 70% of worldwide freshwater withdrawals and 90% of consumptive water consumption are attributed to the agriculture sector (Döll 2009). Food production is also strongly associated with synthetic fertilizers, containing infinite natural resources such as phosphorous (Dawson & Hilton 2011). Moreover, the use of synthetic fertilizers has negative impacts on biodiversity and water quality. In reality, the resources used to produce food that is subsequently lost or wasted account for about 4.4 gigatons of greenhouse gas emissions (CO₂ equivalent) yearly. As a result, it is estimated that food loss and waste is the world's third largest carbon emitter, behind only China and the United States (FAO 2013; Rezaei & Liu 2017).

Some studies have investigated the loss of food and its consequences for natural resources and the environment (Kummu et al. 2012; Porter et al. 2016). For instance, Grizzetti et al. (2013) established that food waste is substantially responsible for a massive increase in anthropogenic nitrogen input to the environment, with negative impacts on human and ecosystem health. Kashyap & Agarwal (2020) studied the land, water, and carbon footprint of India. Sun et al. studied the effect of food waste on the environment in China (Sun et al. 2018). Vilariño et al. (2017) examined food loss and waste reduction as an integral part of a circular economy. Xue et al. (2017) noted that most studies on food losses have been done in a few industrialized countries and highlighted the need for the same in developing countries to achieve SDG 12.3.

In the sub-Saharan Africa region, specifically East Africa, most researchers have studied the post-harvest losses of particular crops, for instance, cereals (Zorya et al. 2011), tomatoes (Sibomana et al. 2016), and bananas (Kikulwe et al. 2018). Other studies have focused on the food security financial losses and ways to reduce the food losses in the sub-Saharan region (Nguz 2007; Affognon et al. 2015; Mvumi & Stathers 2015; Aragie et al. 2018; Aragie 2022). The study of Nzudie et al. (2020) modeled and forecasted root and tuber losses and examined the resulting water losses in sub-Saharan Africa considering climate variables. However, it is noted that no study has tried to investigate the impact of plant-based food losses in the East African community. The study is significant because the region is the water tower source of the Nile, so water-saving techniques and non-point pollution control are paramount to the existence of the Nile River. More so, the region is classified as water-stressed, especially in Kenya and Northern Uganda.

Therefore, our goal is to assess the impacts of the actual food loss on the water resources and the fates of the water environment and carbon emissions in East Africa. Specifically, the study aimed to (i) analyze the actual food consumption and food loss of major food varieties in East African countries; (ii) evaluate the ineffectively used and wasted water resources arising from the food losses; and (iii) evaluate the impacts of food loss on the water environment and carbon emissions. The empirical results obtained in this study on the quantity of water wasted and a negative effect on the environment embedded in the food lost will help create awareness and provide the scientific basis for formulating the policies.

The concept ‘food loss’ refers to the quantity of a product that leaves the supply chain and is not diverted to other uses. Loss occurs as a result of an involuntary action and can occur at any point along the supply chain, from harvest to (but not including) the retail/consumption stage. The study calculates the wastage of major plant-based kinds of food as shown in Table 1 according to the food consumption data obtained from the food balance sheets of three countries in East Africa (Kenya, Tanzania, and Uganda). The year evaluated in the research is 2017.

The data used in the research were obtained from Enhanced Food Balance Sheets for Kenya, Uganda, and Tanzania compiled by the Kenya National Bureau of Statistics (KNBS), Uganda Bureau of Statistics (UBS), and National Bureau of statistics – Zanzibar, respectively.

Among the food varieties, cereals contributed the largest wastage of water resources, 52, 48, and 32% in Kenya, Tanzania, and Uganda. Pulses led to most water resources wastage, especially in Kenya and Uganda, where they accounted for 35 and 22% in the two countries, respectively. The contribution of water wastage due to oil crops loss was also high in Tanzania (32%) and Uganda (21%). Fruit's losses had significant water wastage to contribute to more than 10% in Uganda and Tanzania.

The grey water footprint is an indirect way of using the water resources to assimilate the pollutants arising from the production of crops. Fertilizers are commonly used in excess in an attempt to obtain the maximum yield of the produce. The results show that 404.4 M.m³ of water resources was used to assimilate pollutants in Tanzania as illustrated in Table 3. The amount of grey water in Kenya and Uganda was 317.2 and 116.5 M.m³. The cereals accounted for 65% of the grey water footprint in Tanzania. This is due to high cereal products in the country and grains demanding many water resources, mainly contributed by maize and wheat products. In Kenya, pulses and cereals contributed a large amount of grey water, accounting for 90%. The pulses in Uganda were the primary source of grey water (52%), followed by cereals at 30%.

The total carbon emission as a result of food loss was 5.53 million tons. The carbon emission was largely contributed by Tanzania (3.46 million tons), where the contribution of carbon emission associated with the food loss in Kenya and Uganda was 1.37 million tons and 0.7 Mt, respectively. Cereals were the highest contributor to carbon emissions, contributing 76% in Kenya and 61% in Tanzania. In Uganda, the carbon emissions were mainly contributed by cereals, oil crops, and starchy roots (39, 38, and 8%, respectively). The contributions by the fruits, pulses, and vegetables varied between 1 and 5%, except the vegetables in Tanzania which was 15%.

More than 820 million people are still hungry in the world today, highlighting the enormous difficulty of reaching the Zero Hunger goal by 2030. Hunger is spreading in essentially all of Africa's subregions and to a lesser extent in Latin America and Western Asia (Organization 2019). Because of this and the increased intake of calories and more complex foods that come with rising prosperity in the developing world, agricultural production is expected to increase by about 70% by 2050 (IDA 2020). Every year approximately 1.3 billion tons of food is wasted or lost globally. The trend encourages natural resource overconsumption.

The plant-based food loss in East Africa was 4.50 million tons. The percentage of the food loss was 9, 13, and 6% in Kenya, Tanzania, and Uganda, respectively. The percentage loss of cereals and vegetables was high in Tanzania, represented by 20 and 18%, respectively. In Kenya, 12% of cereals was lost, the same as the pulses. However, in Uganda, the most lost food crops were oil crops and pulses. The cereal loss in Uganda was 7%, similar to the studies of Kaminski et al. (Kaminski & Christiaensen 2014), which estimated the loss of cereals in Uganda to be approximately 5.9%. It is notable, however, that the food loss substantially differs from one country to another. The variance could be attributed to the climatic conditions in the year and the loss due to the level of the infestation (Costa 2015).

The per capita food loss in East Africa was 18–30 kg/year and is very low compared to the estimation obtained by Gustavsson et al. (2011a, 2011b), who revealed that food losses and waste are about 160 kg/year per person. The variance is because our study: (a) revealed that specific food lost differs, (b) our study focused on the actual reported losses, not the estimated, and finally, (c) our system boundary did not include the food waste. Cereals were the main food lost in the region, especially in Tanzania and Kenya, where the loss was 55 and 56%, respectively, in each country of the total food lost. Due to dietary differences in the countries, Uganda's cereal loss was only 31%, and the main food loss was starchy roots at 34%. The other food loss was the pulses, fruits, and vegetables. The loss of these kinds of foods was 9–17%.

Food losses often lead to wastage of the water resources associated with producing the lost food in the supply chain. The water footprint of food loss is the product of the portion of food consumption and the food water footprint per unit. Therefore, the water footprint per unit of food lost is significant for reducing the overall water footprint used in agricultural activities. Globally, food waste contributes 550 billion cubic meters of water losses globally (FAO 2020). The agricultural sector accounts for over 70% of global freshwater withdrawals (IDA 2020). The total green water resources lost in east Africa was 3,008. 0 M.m³. It is noted that there was a significant variation from one country to another as well as whether the water resources are blue or green. The variation in water footprint can be attributed to differences in natural conditions, agricultural production technology, types of food consumed, as well as their susceptibility to losses in the production chain.

The agricultural production in East Africa is heavily dependent on rainfall and, in some instances, flood irrigation. Kenya, which has the least precipitation in the region, wastes more than twice (58%) the blue water compared to the other countries. To reduce the water footprint of agricultural production, mitigate impacts of climate change and improve agricultural production levels, water-saving irrigation is the most important, especially in Kenya. The proportion of farmers using water-saving irrigation inland areas is relatively low. The agricultural water-use efficiency is low; hence, curbing the water lost through the food losses is critical in the East Africa region.

Grey water is an indicator of pollution and an indication of the technological level of a country or a region's agricultural production (Zhang et al. 2019). In Kenya, less than 20% of the land is suitable for crop production as the rest is semi-arid. In Tanzania, however, more than 85% of the land is ideal for crop production. In Kenya and Tanzania, cereals were the primary source of grey water. However, Tanzania was proportionately higher (65%) in comparison to Kenya. Cereals, especially maize and wheat, have a high grey water footprint, indicating that the nitrogen fertilizer application rate and leaching rate are high, resulting in substantial non-point source pollution. Pulses were the main contributor to the grey water in Uganda and Kenya, contributing more than 50%. In Kenya, pulses contributed 48% of the grey water use. The grey water is relatively high in Kenya (15%) and was lowest in Uganda (3%) compared to the total yield of production and food loss. Other studies have noted that chemical fertilizers, manure, and leguminous crops have all played important roles in agricultural intensification. However, they have caused widespread nutrient pollution and the deterioration of lakes, rivers, and coastal waters.

Furthermore, nitrous oxide emissions from fertilized fields contribute to climate change (Foley et al. 2011; Sun et al. 2015). This results from the unproductive nature of Kenya's land, as most arable land is semi-arid, leading to farming intensification of the small available land. This results in a lot of fertilizers having to be applied to increase the yield, hence the higher grey water.

Agriculture has emerged as a significant contributor to global greenhouse gas emissions. Quantitative analysis of the food wastage was conducted using the carbon emission factor (CEF) of food and food loss. Cereals contributed to the most carbon emissions in Kenya and Tanzania, at 76 and 65%, respectively. This is because maize and wheat products are the staple foods in the countries. In Uganda, the contribution of cereals to carbon emission was moderately low, and the contribution by the starchy roots and oil crops was quite significant. Carbon intensity in Uganda was low because its main foods, plantains, cassava, groundnuts, and sweet potatoes, require a low carbon footprint. The finding was in agreement with FAO (2013) that the carbon footprint in the Sub-Saharan region is low due to a starchy diet. Uganda thus is preferable to have the lowest carbon as illustrated above. Other studies have shown that animal-based foods' carbon footprint is higher than plant-based (Cai et al. 2019). However, the same cannot be compared because it is out the system boundary of this research.

Tackling the food loss emerges as an option to mitigate climate change and land degradation and improve global food security and responsible production and consumption within the Sustainable Development Goals (SDGs). Specifically, SDG target 12.3 aims ‘to halve per capita global food waste at the retail and consumer levels and reduce food losses along production and supply chains, including post-harvest losses’ by 2030. Reducing food losses and waste would provide similar benefits for food security as increasing grain yield or total production can relieve pressure on water, land, and the environment. In East Africa, the reduction of food loss is critical in reducing the water resources footprint and reducing the emission of greenhouse gases (GHGs), thus slowing the pace of climate change and downscaling the natural resources use.

It is crucial to recognize that the environmental impacts of food loss extend beyond the direct loss of edible food. The food production process involves various practices, overuse of pesticides and fertilizers, inefficient irrigation methods, improper disposal of agrochemicals, soil erosion and degradation, deforestation, and the conversion of wetlands and other natural habitats into agricultural land. Additionally, inadequate management of livestock waste and the use of large amounts of water in food processing and packaging also contribute to water wastage and environmental pollution in agriculture.

This research examined the implications of food loss on water resources and the environment in East Africa based on the documented food loss from the production in the respective countries in the year 2017. The total water resources wasted due to food loss were 6,164.1 M.m³. Cereals accounted for more water wastage in Kenya and Tanzania. Though the starchy roots and tubers were the most lost food type in Uganda, they only accounted for 10% of the water wastage. It is evident that the staple foods consumed in Uganda are generally low in carbon and consume relatively low water resources per capita. Cereals and pulses significantly impacted the water wastage in Kenya and Uganda, accounting for 35 and 22%, respectively. In addition, the loss results in significant greenhouse gas emissions and non-point pollution of water resources, with a grey water footprint of 838.1 and 5.53 Mt of carbon emissions.

Reducing food loss is of paramount importance for promoting sustainable food systems, particularly given the significant negative environmental impact of food waste. While adopting a low carbon food diet can be a significant step in the right direction, it is important to acknowledge that food loss rates and their environmental impact can vary considerably across different types of food, countries and regions. As such, a localized and tailored approach to reducing food loss is crucial to minimizing its environmental impact and promoting sustainable food systems, while also ensuring the availability of nutritious food for communities.

All data for the actual food losses used in the Manuscript was obtained from Africa Food and Development Bank (AFDB) Database. Kenya food balance sheet https://www.afdb.org/sites/default/files/documents/publication//food_balance_sheets_kenya_full_report.pdf; Uganda Food balance sheets https://www.afdb.org/en/documents/uganda-food-balance-sheets-report-2013-2018; Tanzania Food Balance Sheets https://www.afdb.org/en/documents/tanzania-national-food-balance-sheets-report-2014-2017.

The authors declare there is no conflict.