Assignment 3: Household Metabolism

13 Mar

CM P3200                                       Assignment 3: Household Metabolism

Over the next few classes, we’ll be studying the flows and cycles of materials and energy through systems, essentially system metabolism. The metabolism concept originates at the cellular level within living things – it is the burning of energy in the form of sugars to do the cell’s work of maintaining and growing the body. We often expand it to the level of a whole organism, saying “I have a slow metabolism”, for example. In urban ecology, there is an area of study that looks at the metabolism of entire cities. For this assignment, we’ll look at some aspects of metabolism at the level of the household.

In the diagram below, you’ll note that this is essentially a version of our box-and-arrow diagrams from class. The central box is the house, with input and output arrows. The units of measure for metabolic studies tend to be energy, materials, or water. The critical importance of metabolic studies is that they provide an accounting of fundamental processes that are largely invisible and unnoticed otherwise, and they allow us to tailor our behaviors and technologies toward more sustainable metabolic models. For this assignment, you will do some very simple metabolic accounting for your own household.


  1. Start by identifying your “household” and the way you’ll measure metabolism. This will vary a lot depending on where and how you live. For example, much of the data you might use comes from monthly utility bills. If you are a renter, your utilities may be folded into your rent so you won’t have access to those. If you decide to look at food or other materials, this will be more complicated the more people live in your household, as this will require some cooperation from your fellow household members and tracking things like grocery shopping. Create a box-and-arrow diagram showing your household “system”, what you’re going to measure, and its pathways through your system. For example, here’s one I put together for my household. I chose to do water because I have access to our monthly water bills going back several years and, living in Utah, I’m very interested in water’s role in urban ecological systems.
  2. Once you know what you’re measuring, you need to come up with a data collection sheet. Mine, again, is simple. I created a spreadsheet into which I can enter the amount of water used each month (from my water bill) and the amount of precipitation for that month from NOAA weather archives at (I will need to do a little math to convert the total precipitation depth for each month into a volume for my whole property.)
Month/year Total water use (gal) Precipitation depth (ft) Area of lot (sq ft) Precip volume (=depth*area)

Note that I don’t have any data on the outflow quantities, but I can probably separate indoor use from outdoor use by comparing summer months (when I water the yard) to winter months. However, I can probably keep track of some of the indoor uses (which pretty much all go to the sewer outflow) by tracking how many showers we take, how often we run the washer and dishwasher, etc. That would be a separate data sheet that might look like this

Water use Sunday Monday Tuesday Wednesday
dishwasher (est 20 gal) 1 0 1 0
# showers (est 30 gal) 3 1 2 4
washing machine (est 10 gal) 3 0 0 0
# toilet flushes (.6 gal) 10 6 8 5
water houseplants (2 gal) 1 0 0 0

I’m wildly guessing here how much water these use, but you can look this stuff up online.

If you decide to look at food, or some other material, you will want to track quantity in (most food comes with a weight printed on the label) and quantity out (in trash, you don’t have to weigh it though, or compostables).

  1. Collect your data. If you are using household bills, cover as many months, up to a year, as is convenient. If you’re tracking food, cover at least a few days, preferably a week. It will be easiest if you line it up with trash pickup day, so you can match your input measurement days with a week of trash output.
  2. As best you can, given the data you’ve been able to collect, put some numbers on your diagram. You should at least be able to give numbers to the main input arrows and have some idea of what’s going on inside the system. For example, you may be able to say that half the water used in the house is going to bathing, or that a third of the food is being consumed by your greedy younger brother and that 10% is wasted (gets thrown out). Create another diagram with all the data you’re able to pull together, and write a short report (200-500 words) on what you found out about your household metabolism. This may include any other graphs you might want to create to summarize your findings.

TO HAND IN: Two box-and-arrow diagrams, one with your flowpaths and one with your data, your completed spreadsheet(s), your report.

GRADING: You’ll be graded primarily on having a well-thought out diagram and data collection plan. Additional points come from follow-through (actually managing to collect the data) and the insights you present in your report and final diagram.

NOTE: if you have a household situation in which it will be difficult to find a way to do this, talk to me and we’ll figure out some options. It may involve having yourself as the metabolic unit of measure, rather than the household.

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Posted by on March 13, 2018 in academic writing, Academic Writing



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