Cool Room Insulation
A Project with
Mitchell Gubbins
Adrianna Amsden
March 18, 2014
Abstract
To address high percentages of losses in transporting produce to regional markets, a cool room chain is being implemented in Western Kenya. These cool rooms will serve as temporary storage facilities at locations where losses are occurring at the highest rates. Our team analyzed possible insulation materials for these cool rooms, comparing locally sourced materials to standard imported insulation available in Nairobi. The most viable options locally are rice hulls and corn husks, though other materials could be viable with testing. Either used as a loose fill or processed into panels, these materials have been shown to have insulative properties comparable to standard panels. While the infrastructure for processing rice hulls into corn husks is not currently in place, if implemented, this labor could create an economic opportunity in the form of an insulation business. Overall, further testing is necessary to determine the practicality of each material and construction method, but locally-sourced, agricultural waste insulation is worth investigating further.
Introduction
Currently, horticulture makes up a sizable portion of Kenya’s economy. However, the industry faces large losses of crops due to storage problems. A collaborative project through UC Davis Horticulture Collaborative Research Support Program (Hort CRSP) and the University of Nairobi is aiming to install a cool chain for the storage of fresh produce during transportation to regional markets. Currently, produce is moved by bicycle at night, to avoid sun exposure, but the transportation takes three to five days, during which substantial losses occur. For our research, we were told to assume that new structures were being built for the cool rooms, using cinder blocks or dual layer brick walls. These walls would need to be constructed or retrofitted with insulation. The rooms would then be chilled using a CoolBot system.
Our goal is to find and compare locally available insulation materials to optimize the efficiency of these cool rooms, while also taking price, labor, safety, and sustainability into account. This will allow farmers more control of their produce, minimize product losses, and allow potential reuse of waste materials. We aim to provide a comparative analysis of materials as well as recommendations for moving forward with the project.
Background
Kenya is a country approximately double the area of Nevada on Africa’s East coast. It is bordered by the Indian Ocean to the east and Lake Victoria to the west, as well as Tanzania, Sudan, Uganda, Ethiopia, and Somalia. With a population of 41 million, it is estimated that one third of Kenyans live in urban areas, which is attributable to its significant agricultural sector. Western Kenya is comprised of highlands, as shown in Figure 1 of the appendix, which make up one of the most agriculturally successful regions of Africa. Despite this, 38% of Kenyans live in absolute poverty. Agricultural exports contribute 22% of Kenya’s GDP, though 75% of the workforce is employed in the trade. This inefficiency is common in countries which lack food security. For contrast, developed, food-secure nations on average employ just 3% of their population in agriculture. Kenya’s economic reliance on agricultural exports also put the country at the mercy of rainfall conditions and international market prices.[1]
While Kenya’s agriculture makes up much of the country’s exports, half of the agricultural production is for subsistence purposes. This results in a reliance on predictable rainfall, as the country lacks much developed irrigation infrastructure. Kenyans practice both conventional and organic growing, though there has been an increase in pesticide use in the last decade. Farmers struggle with crop losses to diseases and beetles, particularly weevils. To combat this, some farmers have begun experimenting with planting rice near sweet potato crops, which was shown to reduce damage from weevils to the potato yield. Additionally, attempts have been made to plant millet in with the sweet potatoes, which has been effective in reducing damage, but severely reduces the yield. Further, growth of weeds can reduce yield by as much as sixty percent. Weed control is labour intensive, motivating farmers to seek out herbicides.
In addition to crop loss in the fields, farmers face significant losses while transporting their produce to regional markets. A lack of transportation infrastructure has led to most produce being moved by bicycle during the night to avoid direct sunlight on products. This process is slow, often taking anywhere from days to a week to reach markets. Postharvest losses in Kenya vary by region, based on the available infrastructure. In Western Kenya, losses are estimated around 14% for rice.[2] Jane Ambuko, a Horticulture Lecturer at the University of Nairobi (with whom my group is in contact) estimates postharvest losses vary anywhere from ten to fifty percent, depending on the type of produce.
The solution currently being pursued is the implementation of a cold chain. Hofstra University researchers Dr. Jean-Paul Rodrigue and Dr. Theo Notteboom work on cold chain analysis. In their paper, “The Cold Chain and its Logistics,” they write, “The cold chain involves the transportation of temperature sensitive products along a supply chain through thermal and refrigerated packaging methods and the logistical planning to protect the integrity of these shipments.” The implementation of such infrastructure is supported by many researchers, including Jane Ambuko. During the Africa Food Security Conference, Ambuko was quoted as saying, “Kenya should therefore adopt temperature management practices especially for horticultural produce in order to curb the huge losses.”[3]
There are many factors to be considered when implementing new technology or techniques to curb postharvest losses. One of the major factors are constrictions on labor and capital resources. Methods that require drastic increases in either of these are unlikely to be widely accepted. Similarly, previous studies on FAO projects suggest that presenting a new method as a singular solution is met with resistance. It has been theorized that new methods would be met more positively if they built on current methods and offered a range of techniques for farmers to choose from.[4]
However, most of these methods are focused on the long-term storage of grains. For fresh produce, storage is in the range of days to a week, meaning that instead of dealing with pests and disease, the freshness and damage to the product are of more importance. Products left in the sun can reach 13-16°C above ambient temperature. For every ten degrees, a products post-harvest life is halved.[5] Thus keeping produce out of the sun is the first step. Even better is keeping a product below ambient temperatures, which in Kenya are higher than optimum storage temperatures for produce. It is for these products that cool chains are implemented. For optimized cost-effectiveness, cool rooms should be built in places where A) the most damage occurs and B) the most produce is passing through on its way to markets. If placed at these vital junctions, losses to heat and sun damage will be minimized, allowing farmers to yield higher profits from their produce.
Methodology
The goal of the Kenya Cool Room Insulation project is to complete a feasibility study for our client and make a recommendation to them for the insulation method they should utilize in the construction of cool rooms for storing produce. It follows that research into different insulation materials and methods would be an integral part of this project. Fortunately for our group, insulation is an important topic worldwide so there has already been research done in the field. The overall goal of our research into insulation materials is to identify possible materials, develop criteria to test their effectiveness and viability, and then evaluate the materials to make a recommendation for the most appropriate insulation method. So far, the most promising material for use in Kenya seems to be rice hulls, with corn husks as a close second.
For this project, one of the goals is to also look beyond more traditional insulation materials and explore more novel materials. The type of materials we are most interested in exploring are agricultural waste materials such as rice hulls or oil palm leaves. Using agricultural waste instead of more traditional insulation methods (such as expanding foam or fiberglass fill) may have several possible benefits. Agricultural waste could possibly be cheaper than industrial materials, have less of an environmental impact (or a perhaps a positive impact), or even allow the creation of a new local business processing otherwise wasted materials into a useful product. However, these benefits would mean nothing if agricultural waste doesn’t work as an insulation material. Thus, criteria had to be developed to evaluate agricultural waste’s viability as an insulation material.
Particularly useful in our research was the study “Agricultural Waste Materials as Thermal Insulation for Dwellings in Thailand: Preliminary Results,” done by researchers at the University of Sheffield [6]. The paper was presented at the conference on Passive and Low Energy Architecture in Dublin and explores the feasibility of usage of various agricultural waste materials as insulation. This study was very helpful for us when evaluating possible raw materials as it gave examples of agricultural waste that could be used, developed criteria for comparing it to traditional insulation methods, and provided us with an example feasibility study to reference when doing our own.
The study identified various different agricultural waste materials as potential insulation materials. These potential materials were chosen for a variety of reasons explained by the paper, which helped our team to come up with potential agricultural waste materials to evaluate in our study. The researchers started by first thinking about the setting in which their insulation would be used and the needs of the population. The study was done in Thailand focusing on urban dwellings in Bangkok. This gave the researchers a set of parameters to work in; the insulation materials had to work in a hot, humid climate providing ventilation and resistance to moisture. Although Kenya’s climate is different than that of Thailand, the parameters for selecting our insulation material are similar as the requirements of our insulation are alike. The researchers also needed to consider local and global availability of the material when choosing possible materials to make sure that the materials could be sourced for use in construction in Thailand. Finally considered were the environmental impact of each material to see if they would be better than typical, industrial insulation. This part of the study gives us the factors to examine when picking materials to be tested: the setting they will used in, their intended use, local availability, and the environmental impact they will have.
After picking the potential materials, certain physical properties of each must be tested to determine if they will work as insulation. This is a very important factor in evaluating possible materials as these physical properties determine whether or not the agricultural waste will function properly as insulation. The biggest and by far most important property when assessing these materials is their thermal conductivity. Thermal conductivity is a measure of the amount of heat transfer a material allows at different temperatures, or in other words, how well heat can flow through the material. For insulation materials, it is important to have a low thermal conductivity. The lower the conductivity the better the material acts as a barrier from temperature changes outside of the insulated structure. The material’s density is another property that matters as in typical insulation applications one only has a finite amount of space in which to fit insulation material. These two important properties of insulation materials are combined into the R-value, which is used to easily and quickly compare the thermal resistance of different materials. The higher the R-value, the better the material acts as insulation. The results of testing the agricultural waste materials in the Thailand study are compared to typical insulation material properties in the figure to the left, where it can be seen that many agricultural waste products fall into the normal range of thermal conductivities and densities of usual insulation materials [6].
While these properties determine the material’s insulation performance on paper, the material’s actual effectiveness as an insulator (especially for our intended use in Kenya) is determined by other properties that protect from the environmental factors the insulation faces. In addition to isolating the interior from temperature change, insulation materials can help to protect the interior from other aspects of the environment outside. A major one is moisture protection. This is important as it controls another component of the interior climate (moisture/humidity) helping to keep optimal conditions for the storage of produce. Protection from moisture is also important as absorbing moisture can ruin the performance of insulation material. As it is installed in the entirety of the structure, insulation plays a large role in determining the safety of the building it is installed in. It is important then, that an insulation material has some resistance to fire and mold as if it is highly susceptible to either that provides a huge concern for the safety of both the structure and its contents. When evaluating agricultural waste and other alternative forms of insulation material, we need to consider if the material has a thermal conductivity, moisture protection, and fire/mold resistance comparable to or better than those of traditional insulation materials.
Once those properties are measured and potential materials are chosen, it must be determined how the raw material will be processed and installed. It doesn’t matter if one finds the perfect raw material for insulating if that material cannot be processed into a usable form or installed. It is important then to find a method of processing and installing the insulation that is feasible in context of its application.
The two construction methods we considered were a loose fill of the raw material as well as processing the raw material into panels. These methods were chosen due to the fact that they are already generally accepted methods of construction and relatively simple compared to methods such as spray foam. Loose fill and processed panels have different advantages and disadvantages over each other, making them more appropriate for different building construction methods. These will be discussed in the results section.