demand. In 2010, India consumed around 65 billion cubic meters of natural gas, of which 12

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1 Team Biopower E/Me 105 March 4, nd Term Final Report I. Problem Statement India has the one of the largest populations in the world at over 1.2 billion people, which is growing steadily at around 1.3% per year. With the rapidly increasing population comes a huge demand for energy and fuel. India has come to rely on imports to meet this Figure 1 : Garbage lying on streets demand. In 2010, India consumed around 65 billion cubic meters of natural gas, of which 12 billion cubic meters is imported. The desire for a higher quality of life further increases the demand for energy sources. In addition to struggling to meet its energy needs, India is struggling with waste management. Because no waste management system exists in most places, garbage is often abandoned on streets (See Figure 1). Biogas plants can help India address the aforementioned problems, but they are not yet popular enough to make a significant impact. Biogas plants in India vary significantly in design, from big ferrocement plants to small plastic plants. However, regardless of size and material, these biogas plants are not Figure 2: Woman using wood to cook yet popular in homes due to their high cost, low production rates, and required daily use. Companies claim that the tanks will pay for themselves in two to three years, but this does not appear to be a sufficient motivation for consumers because the cost of capital investment is still high. Cost was the biggest complaint in interviews with

2 consumers who do not yet own tanks, as the cheapest biogas tanks available in our region of interest, Kerala, were Rs. 13,500 (~$250). In addition to the cost, our interviews with the biogas plant owners revealed that maintenance is a major issue and that customers are also unsatisfied with slow gas production. Our interviews revealed that the users were not able to completely replace cooking gas with biogas, typically only producing enough gas Figure 3: People waiting in line for gas for up to two hours of use from a cubic meter tank taking six to seven hours to regenerate. If the plant is not used for a few days, it ceases to work properly because water condenses in the gas pipe and blocks it. This makes the plant less appealing for individual homes, where the tanks may not be used regularly. Cost, maintenance, and efficiency are three major obstacles preventing consumers from purchasing biogas tanks. India has large scale problems with finding energy sources and dealing with waste management. With the high potential for improvement of the individual biogas tank, Biopower is developing a product that will help the at home biogas tank rise to prominence. This term, we are working on producing a new biogas tank design that will address issues that are preventing more consumers from buying tanks currently on the market. II. Market and Consumer Most biogas producers concentrate on big customers like hotels, hostels and hospitals and do not market towards smaller households. We are carving a niche for ourselves by concentrating on smaller, rural households. These families are particularly ideal targets for biogas tanks because they need both gas for daily cooking and fertilizer for their farms.

3 However, because most Keralites spend $12 per month on LPG gas, biogas tanks take many years before they pay for themselves. Although the producers we talked to sell around 200 units a month, there are almost 30 million people in Kerala, so there is still a greater market to reach. III. The Switch from Prior Work Despite the benefits of using a biogas tank, many Indian households have not adopted them into their lives. Because of their high price, low efficiency, and need for daily use, customers in Kerala are reluctant to purchase the tanks. Last term, we decided to tackle the problems concerning efficiency. Large scale biogas tanks often employ a shredder that shreds the waste input into smaller pieces. By increasing the surface area of the input, the waste will be digested faster and the overall efficiency of the tank will increase. To quickly test this idea, we conducted an experiment comparing the Figure 4: Experiment showing gas production differences between shredded (left) vs. non shredded (right) input results of gas production from shredded input compared to regular input (See Figure 4). Shredded waste was put in one bottle and non shredded waste in another, and deflated balloons were secured on the bottle neck. Because the balloon on the bottle with the shredded waste became larger quicker than the other balloon, it was evident that shredding the waste increases gas production efficiency.

4 Unfortunately, the biogas tanks on the market meant for household use currently do not employ this feature; waste is inserted into the input pipe with little to no processing. Therefore, we wanted to apply the shredding tactic from large scale biogas tanks to smaller tanks to improve their efficiency. After a couple weeks of brainstorming, we developed a waste shredder that would be placed at the input pipe and shred incoming waste by a hand crank like Figure 5: Our waste shredder from first term a garbage disposal (See Figure 5). However, we eventually realized the inefficiencies of building our own shredder. Compared with existing food shredders on the market, our shredder was bulkier, less efficient, and most importantly, more expensive. Despite the potential gain from incorporating a waste shredder, the price tag of our device was significantly greater than similar products on the market (like a manual food shredder available on Amazon). Additionally, by introducing a new dimension to the previous biogas tank, we were also introducing new complications such as maintenance issues (What happens if the blade breaks? How will the user clean the shredder?) and social issues (Will the people of Kerala be willing to take time off to manually shred waste? How do we prevent children from accidentally hurting themselves?). As the cons started to outweigh the pros, our waste shredder looked less marketable, although the concept did prove to increase efficiency. At the start of the second term, our team decided to stop building our own waste shredder. Even though we still wanted to incorporate the idea of shredding input into the small scale biogas

5 tanks, we felt it was more beneficial to use food shredders already on the market and focus on improving biogas tanks in other ways. Once again, we wanted to focus on the three biggest complaints from our interviews: cost, efficiency, and maintenance. After much debate, our team voted on building our own biogas tank that would be more appealing than tanks currently on the market. IV. New Product Design The challenge then became coming up with new innovations that would put our product ahead. In deciding what biogas tank model we wanted to iterate upon, our team did research on preexisting biogas tanks. We discovered there are dozens of designs, with the major ones being ferrocement tanks, floating drum tanks, and balloon tanks. After interviewing local producers in India who distributed ferrocement and floating drum tanks and completing secondary online research, we concluded that the floating drum model was the cheapest and most efficient of the existing models and plausible to produce in Kerala with a manufacturer. In the region we worked in, ferrocement tanks cost Rs. 20k 25k (~$400) and the floating drum tanks cost Rs. 13.5k (~$250). This difference was significant enough to push us towards the floating drum model. Within the line of floating drum models, the team still had to decide whether to use a single wall or double wall design. In general, the floating drum model consists of a waste tank and a gas tank that floats upside down over the waste. The gas tank then rises when the waste produces gas, thereby maintaining constant pressure (~30 50 psi, depending on if weights are placed on top of the gas tank).

6 Figure 6: Differences between double wall and single wall In the single wall design, the gas tank floats directly in the waste slurry (See Figure 6). In the double wall design, there is an additional wall around the gas tank that holds a water jacket that the gas tank floats in instead of the slurry. There are advantages and disadvantages between the two models. The single wall design requires less material for production, which reduces the cost, but also allows leakage of gas production as the tank holding slurry is not enclosed entirely by the gas tank. This makes the single wall design less efficient by up to 25% and more likely to emit unpleasant smells. The double wall design requires more material and is thus more costly, but collects the entirety of the gas produced and keeps the slurry enclosed. We decided to use the double wall design because we felt that keeping the waste completely enclosed was vital if we want our product to be sanitary and appealing, and because we did not want to lose efficiency.

7 Once the general model of the tank was decided, we wanted to address cost, efficiency, and requirement of use. After recognizing that the fiberglass material for the tanks themselves was the greatest portion of the production cost, we decided that reducing the size of the tank would be the simplest way to reduce the cost. The ideal tank size would be 700 L, instead of the typical 1000 L tank that currently dominates the market in India. In order to improve efficiency, the commercial waste shredder from first term could be implemented and attached to the input pipe of the tank. To address the issue of condensation Figure 7: Our design for biogas tank build up in the gas pipe, which occurs when the tank is not used daily, we came up with a split gas pipe design (See Figure 7). The split gas pipe would allow the condensation to drip down to the waste bucket in a lower pipe while keeping the upper pipe free for gas flow. The combination of these three features would make our tank better than the standard floating drum tank in the market. V. Initial Prototypes Before building a full sized model, the US team built a rudimentary prototype to prove the efficacy of the double wall biogas tank. The purpose of the experiment was to quickly test whether our design for a biogas tank would produce and retain gas.

8 The inner tank was approximately 10 L and the outer tank was approximately 20 L. Below are photos of the tank: Figure 8: First US prototype On the left, we have placed the inner tank into the outer tank and filled both tanks with water. Next, we added shredded food to the prototype s inner tank. Finally we placed the top on the inner tank. This seals the tank and allows gas to build up. For our initial prototype we provided no method to add or remove waste or siphon off gas. We just wanted to test our design s ability to produce the gas. The top rose 5 in about 2 weeks, which indicates that we produced and retained gas. Simultaneously, the Indian team built a prototype in Kerela, India. The purpose of this prototype was to have a biogas tank in India and to get feedback from manufacturers on the design. Below are photos of the design: Figure 9: First Indian Prototype The photo on the left is the tank without a top on it (the blue structure at the bottom is a stand. The middle photo is a view inside the tank. The right photo is the tank with the top on it. The tube coming out of the top of the tank is the gas output tube. This is made

9 entirely with local plastic parts. This tank is very similar to the US rudimentary prototype, but our team felt it was important that there was a prototype in India as well. VI. Functional Prototype During the last three weeks of the term, we built a fully functional prototype using trash cans from Rubbermaid (See Figure 10). Although this prototype would be very different than the molded fiberglass tank that would be produced in India, this tank is still functional and would work similarly. We were limited by available sizes of trash cans in the market, so we ended up building a smaller prototype than what we have hoped. We Figure 10: Functional Prototype, outer view (left) and inner view (right) used trash cans of three different sizes: Outer tank 44 gallon (165 liter), inner tank 20 gallon (75 liter), and gas holder 32 gallon (120 liter). We had the 20 gallon tank stacked inside the 44 gallon tank to form a double wall, and the 32 gallon tank will be on top of it to act as the gas holder. For input and output pipes, we have used 2 PVC pipes, connected with 90 degree bends.

10 Figure 11: Attached Waste Shredder In order to improve our prototype, we added our own innovation the waste shredder at the input (See Figure 11). We used a commercially available food shredder from Kitchen King Pro. We also designed and fabricated our own plexiglass piece using a laser printer to connect the waste shredder to the input pipe. Because the connector is simple and easy to make, we expect this design to be easily modified and applied to other biogas tanks with varying pipe sizes and food shredder designs. Unfortunately, the team was unable to implement the idea of the split gas pipe because the correct piece necessary to allow the gas pipe to branch was not available. The team expected the piece to be a standard item that could be found at the local hardware store, but they were unable to find the correct size even when looking online. Thus, this feature of the tank remains hypothetical. Because our prototype was made out of multiple parts, we were concerned about making the prototype water and gas tight. We used silicon cement to fill gaps between the pipe and the tank walls. When we filled the tank with water to test the seal, however, the inner tank broke loose along with the seal due to its buoyancy. This was due to our different design from other more conventional floating designs in India: the conventional designs have the inner and outer tank connected as one piece, whereas our prototype is formed with two

11 separate tanks connected together. We are hoping to resolve this issue by putting heavy weights inside the inner tank, negating the buoyancy force. VII. Testing During the final week, the U.S. team filled the functional prototype with food waste Figure 12: Testing Final Prototype from a dining hall (See Figure 12). However, the tank leaked when the outer jacket was filled with water. Furthermore, there was insufficient time to allow the gas to produce. Thus, we were unable to rigorously prove the functionality of our iterated biogas tank with testing. VIII. Successes and Shortcomings Team Biogas has had a number of successes. First, we were able to actually produce gas in our initial prototype. We were also able to construct a full scale prototype that could collect biogas. We incorporated several features that would theoretically improve the value of a biogas tank particularly the waste shredder and split gas pipe. On the other hand, we had some shortcomings. We were not able to exhaustively test our full scale prototype because we had issues sealing it to make it watertight and did not have sufficient time to allow gas production. Therefore, there is no formal proof that our tank will be more valuable than existing tanks, which makes it difficult to sell. Additionally, because we did not find our product marketable we did not work very closely with a manufacturer in India. We did get some feedback on our rudimentary Indian prototype, but

12 never a price estimate for the completed design. As a result, we would still need to accomplish a lot of additional work before our tank could be manufactured and sold. Finally, we did very little market research and thus did not realize how competitive the biogas market is. There are many solutions available on the market, some comparable in price to ours. IX. Working with a Manufacturer Our primary contact in the final stages of product development was NELA, Natural Energy for Learn and Action. NELA is a non government and non profit organization that produces floating drum biogas tanks near Kanjirappally, Kottayam. We conducted several interviews with NELA, and they were a great resource for information about biogas tank production in Kerala. They mainly focus on manufacturing and distributing 1000 L portable biogas plants made of fiberglass. They currently have two molds 1000 L and 700 L. However, the currently only produce the 1000 L tanks and do not produce the 700 L tanks. After discussion, NELA was willing to work with us to produce 700 L tanks if we provided sufficient support that we could make the 700 L marketable. However, since we were unable to do this, we did not carry through with the manufacturer. X. Team Dynamics After two terms, we realized that keeping everyone on the same page was our biggest problem. Between obligations to other classes and the time zone differences, scheduling a convenient meeting time remained a challenge; once, the US team and Indian team missed each other by one hour because we forgot about daylight savings. Nevertheless, compared to our meetings first term, we felt we did a much better job arranging meetings as we were more determined to finish our work on time. Unlike first term, we sent multiple s as

13 reminders in case some of us forgot the first time; we also arranged meetings earlier to avoid potential time conflicts with other obligations. On the US side, we also met face to face instead of through Google Chat. This helped us communicate more clearly with each other and we also became more productive. While not necessarily a disadvantage, a unique challenge that we faced was that our team consisted of more non mechanical engineers than mechanical engineers. At first, this was a problem because only one of us was authorized to operate the machinery in the machine shop. Fortunately, we found ways to distribute tasks so that everyone had something to do. Even though some of us could not operate the heavy machinery, we could still help out with building the prototype, such as research, design, buying parts from Home Depot, and small labor tasks such as cutting garbage cans to size using a handsaw.