The Habitat for Humanity ReStore MetroWest/Greater Worcester is a branch of the non-profit organization, Habitat for Humanity, and receives unused or partially used housing materials as donations from individuals, local retailers, and other businesses. It then resells the materials at 50 -75% below retail prices and donates its proceeds to Habitat for Humanity. In this way, the ReStore benefits the environment by preventing a significant amount of materials from being sent to the landfill. It also benefits the community by providing quality and highly affordable building materials to the public.
The ReStore needs grants in order to improve its donation processing system. The ReStore needs a method to estimate the tonnage of materials that it keeps out of landfills as it is essential in applying for grants. Unfortunately, having a floor scale permanently cannot be a solution for estimating tonnage because not only the space the scale will occupy is necessary for donations but constantly collecting weights will slow down the overall donation process.
Therefore, the goal of our project was to develop an estimation method to determine the actual tonnage of materials that are sold at the ReStore. This consequently facilitated ReStore in applying for the grants necessary to improve the current system of donation processing. The project objectives are:
1. Site assessment
2. Data collection
3. Comparison of weight estimation methods
4. Manual implementation
We spent a week at ReStore as volunteers in order to get insights on how ReStore runs and how our project could be integrated into its working environment. After obtaining information during the first week, we started to collect data samples. We collected a thousand data points and created a database based on them; we analyzed our data and derived a formula to estimate the tonnage; and we compared our formulas to find out the more accurate one. Finally, we created a manual that contains step-by-step instructions on how to utilize the weight estimation method and how to update the database in the future. In addition, we also had training sessions for the administration and volunteers to demonstrate our method.
Based on the information we can get from the ReStore sales report, we designed two different method for weight estimation. One is based on the average weight of each department and the other is based on the average sales price of the items in each department. Also, the ReStore currently operates on the idea that for every dollar that is sold, 1.3 lbs. of material are kept out of the landfill in order to estimate weight. We tested and compared the monetary value and weight methods to the ReStore’s current weight estimation method in order to fully evaluate which method is more accurate.
After the best possible method was determined, the administration will be in charge of applying this method to their own database. At the end of each month, a report is taken from the database at the ReStore that outlines the departments, total sales by department, and the quantity of items sold in that month. What we have determined through our calculation is the department weight average and the department conversion factor.
These values are used to estimate weight in two different methods. The weight estimate based on average weight is fairly simple. The estimated weight of a department is calculated by multiplying the department average weight and quantity of sold items. When this calculation is done for every department, the sum of the products is the total weight of items sold during that particular month. The weight estimation based on monetary value uses a similar process. The department weight conversion factor is multiplied by the total sales of that particular department. Since the weight conversion factor has the units of pounds per dollar, when it is multiplied by dollars, a weight estimate is derived. This is done for each department as well. Finally the sum of all of those estimates equals the total weight of items that were sold during that month.
Lastly, we compiled some recommendations for the ReStore to take into consideration. In order to increase the efficiency of future data creation, we recommended that the ReStore change the database systems it currently has in place. Furthermore, to avoid the discrepancy present when placing an item in a department, the ReStore needs to clarify how to classify donations in departments. In order to increase the overall accuracy of the average weights and conversion factors for each department, it is necessary for ReStore to accumulate more data in the future and obtain a larger sample size to reduce the chance of errors. Finally, the ReStore should adhere to the steps we have provided for them to estimate the tonnage of materials the ReStore keeps out the landfill.