School Year Transportation

Since January, I have recorded every time I have consumed fossil fuels to power a form of transportation. I have kept track of what kind of vehicle and I used, how far I traveled, how many people shared that mode of transportation with me, etc. Now, as the school year is coming to the close, I would like to examine some patterns in my chosen transportation methods while I have been a student, and how these contribute to my carbon footprint.

All types of transportation

So far this year, I have traveled a total of almost 7,400 miles in planes (35.7%), boats (for the spring break cruise, 24.4%), cars (39.6%), and public transportation (0.4%). The different carbon intensities of these different modes of travel mean that the distribution of the associated carbon footprint differs slightly in proportion from the distance traveled in each mode:

  • Planes: 487 kg CO2eq, 0.19 kg CO2eq /mile, 24.9% of total CO2eq
  • Boats: 724 kg CO2eq, 0.40 kg CO2eq /mile, 24.4% of total CO2eq (includes ship fuel only)
  • Cars: 738 kg CO2eq, 0.25 kg CO2eq /mile, 37.8% of total CO2eq
  • Public transportation: 5 kg CO2eq, 0.164 CO2eq /mile, 0.4% of total CO2eq
  • Total transportation: 1,953 kg CO2eq

Clearly, my travels on a cruise ship for spring break have had a very significant impact on my total carbon footprint related to transportation.

Miles traveled in a car

Since driving in a car is the mode of transportation I most commonly use (in terms of frequency and number of trips, not necessarily by mileage), I would like to look more in depth on where these miles are coming from. Note that I have included travel in each personal vehicle I have driven or ridden in this semester, not only my own vehicle.

I have collected several pieces of data regarding transportation by car, including year/model/make of the vehicle (to estimate fuel efficiency), miles traveled, and number of people in the vehicle. I’ve also categorized each trip into one of eight categories: school, work, dance, dining/food, travel/vacation, shopping (non-food), entertainment, and miscellaneous. Some data manipulation has revealed a couple trends that I find interesting:

  • Carpooling: About 66% of the miles I have spent traveling in a car have been with at least one other person in the vehicle. However, only about 61% of the total trips in a car (trip defined essentially as one cycle of turning on the engine, driving from point A to point B, and turning off the engine) were with more than one person in the car. From this, I can conclude that I’m carpooling about two-thirds of the time, but I tend to carpool more for longer journeys.
  • Reason for travel: By far, dance accounts for the largest portion of miles driven. This accounts for 45% of my miles driven (the next highest category was miles driven for dining and food, at 20%). This is probably because all of the longest distances I have driven this semester (from Houston to Austin, and from Houston to College Station) have been to travel to and from dance events.

I have also compared my driving habits to habits of an average American. The 2009 National Household Travel Survey includes data on the daily person miles of travel per mode of transportation (including private vehicles). Comparison with my own travel habits reveals I generally drive much less for work and work related business but much more for social and recreational activities, which makes sense given my lifestyle as a student and a dancer.

Predictions for off-campus living

Later this year, I’m planning to re-visit this transportation data and examine how my transportation habits change after I’m not longer living on campus. I would like to make a few predictions:

  • Amount of carpooling will probably decrease, since I will no longer be offering rides to my fellow students who do not have cars
  • Total number of miles driven in a car will probably increase, since I will be commuting to and from work each day.
  • I suspect that I will drive relatively more miles for work and relatively less miles for dance. However, since a significant portion of the miles driven for dance were from driving to Austin and College Station for dance events, and I do not anticipate eliminating these trips in the future, I don’t know that this mileage will decrease significantly.

The Beer Bike Water Balloon Fight

One of the main events at Beer Bike is the full-school water balloon fight, during which hundreds of undergraduates run around Founder’s Court to pelt their friends with water balloons. What is the carbon footprint associated with all of the water and balloons that are consumed on this day?

I estimate that my residential college (Martel College) filled about fifteen 55-gallon trash cans with water balloons in preparation for the biggest battle of the year.

Water: The water filling the trashcans and balloons alone is over 800 gallons of water from the municipal water supply, or 14 kg of CO2 emissions (not even counting water that was wasted while filling and transporting the balloons).

Balloons: The balloons themselves (estimated 5 kg latex) represent another 2.5 kg of emissions, with an emission factor 0.54 kg CO2eq/CO2 latex (for latex produced on long-cultivated lands in Thailand, which is an assumption). This doesn’t even include the carbon involved in processing this latex to form balloons, packaging, and transportation.

 On Campus Transportation: The balloons were driven from Martel College to Founders Court. The distance itself isn’t all that far – maybe three-quarters of a mile one-way if we’re being generous – but it is a factor. Assuming an emission factor of 161.8 g CO2/short ton-mile, transporting the balloons emits 0.36 kg CO2eq.

TOTAL for Martel College water balloon production and preparation: 17 kg CO2eq, or about 40 miles driven in my 2001 Honda CRV. The grand total for the university is at least 11 times this amount (there are 11 residential colleges, most of which fill many more balloons than Martel) – almost 200 kg CO2eq, or 450 miles in my car.

Duct Tape – A Preliminary Analysis

Not only is duct tape a staple in an engineer’s home toolbox, it was likely an integral part of Martel College’s build for Beer Bike this past weekend. Thus, a preliminary analysis of a common roll of duct tape – 1.88 in x 20 yd roll of Duck Tape – is the subject of this week’s post. For such a common, seemingly simple material, the environmental impacts are actually a bit difficult to track down, so I will split this into multiple posts to allow for adequate detail.

These articles from How Products are Made and Sweethome’s review of The Best Duct Tape helped me figure out the basic construction of duct tape: a grid of cotton/polyester blend with a polyethylene backing on one side and a rubber-based adhesive on the other. For now, I’ll focus only on the embodied carbon in materials, not manufacturing, transport, and end of life.

Cotton Grid: For simplicity, I assumed the threads were pure cotton (5.9 kg CO2 / ton spun fiber). Counting 20×8 thread count in a square inch of the tape I happen to have at home, the cotton contributes 0.4 g CO2eq to the carbon footprint of duct tape.

Polyethylene Backing: If the tape is approximately 9 mils thick (mil = milli-inch), and I estimate that the polyethylene (LDPE) backing makes up about 20% of the total volume of the tape, 0.07 kg of LDPE are in the roll of duct tape. Assuming ~1.9 kg CO2eq/kg plastic, this represents about 1.5 g CO2eq.

Adhesive: Duct tape uses a rubber-based pressure sensitive adhesive, a substance that is tacky at room temperature and adheres almost any surface with a very small amount of pressure. Without inside industry knowledge, I don’t know enough about the additives to complete a thorough analysis of the adhesive. For this first-round analysis, I’ll estimate that 65% of the total duct tape volume is adhesive that can be modeled as pure rubber; using a number associated with rubber production in Thailand on previously forested land, 0.1 kg rubber represents approximately 1.5 kg CO2 eq.

Cardboard Roll: After measuring the cardboard roll to be about 3” in diameter and 0.25” thick, I estimate about 0.03 kg cardboard are incorporated into the roll. At 3.31 kg CO2eq/kg cardboard, this equates to 0.09 kg CO2eq.

Preliminary Total: Though there is much work still to be done to refine this total estimate, for now I estimate about 1.75 kg CO2eq per roll of duct tape.

Spring Break Cruise (Part 2)

This week is dedicated to adding more details to my analysis of the cruise. I’ve broken the total carbon footprint into four pieces: ship operation, land transportation, food, and drinks. The total footprint (detailed below) is 778 kg CO2eq, equivalent to driving 1,840 miles in my car.

Ship Operation: In the last post, I discussed three possible carbon footprints related to the ship itself via a carbon calculator (1.1 tonnes), the 2015 Carnival Sustainability Report (0.8 tonnes), and the 2008 Carnival Environmental Management Report (4.8 tonnes). For the rest of the analysis, I’m going to use the 0.8 tonne (1700 miles in my car) estimate; while my intuition suggests this is a low estimate, it’s based on the most recent data specific to Carnival.

Land Transportation: To travel to and from the ship, my friend and I were dropped off and picked up in Galveston. In total, the two 104 mile round trips (one to drop off and one to pick up) in a 2005.5 Mazda 3 (approx. 26 mpg) split between two people equates to 36 kg CO2eq (84 miles in my car).

Food: Of all of the delicious food on the ship, the largest carbon impacts are associated with the meat I consumed on board. I estimate that the beef, pork, and salmon I ate on the ship represents about 19 kg CO2eq (45 miles in my car).

Drinks: According to this study, the carbon impacts of alcohol are pretty small; in this case, the impacts are negligible in comparison to fuel and food consumption.

Spring Break Cruise (Part 1)

This past week, a friend and I went on a cruise for spring break, a 5 day adventure on the Carnival Valor in the Gulf of Mexico. The trip was a lot of fun, but I’m very curious about the environmental impacts of a diesel powered ship with seemingly unlimited food, drink, and overall consumption.

The 2016 Cruise Ship Report Card from Friends of the Earth ranked 17 cruise lines with respect to four factors: sewage treatment, air pollution reduction, water quality compliance, and transparency.  Of the 17, Carnival ended up in the middle of the pack with an overall final grade of D. Carnival’s individual scores broke down as follows:

  • Sewage treatment: F
  • Air pollution reduction: C-
  • Water quality compliance: A
  • Transparency: F

Several webpages and blogs already detail the various environmental affects and concerns regarding these four factors (and more), and I won’t re-iterate all of that information here. Instead, I will specifically examine the carbon footprint associate with my spring break cruise

One carbon calculator for cruises estimates a 1.1 ton CO2 footprint for one passenger on my 5 day cruise. Let’s investigate a little further to understand where this number comes from, and how accurate it may be, beginning with emissions related to fuel consumption.

Method 1: Reported Scope 1 and 2 Emissions

Carnival’s 2015 Sustainability Report provides some information on total CO2eq emissions, including scope 1 and scope 2 emissions. Understandably, most of the emissions come from burning fuel on the ship. Exact numbers were not provided in the report, but I estimated from a graph that in 2015 (the most recent year), Carnival had an overall carbon intensity of 250 g CO2eq/ALB-km (ALB = Available Lower Berth). If the Valor traveled approximately 1800 miles (2900 km) round-trip for the cruise, this amounts to 725 kg CO2 for the trip – just about 65% of the estimated 1.1 tonne footprint from the calculator.

Method 2: Direct Calculation

In an attempt to double check this number, I directly calculated the carbon emissions based on a second set of data. According to Carnival’s 2008 Environmental Management Report, their ship emits 0.33 kg CO2/ALB-km (ALB = Available Lower Berth). It’s not explicit whether this number accounts for the time in which ships are docked at port and still burning diesel to power the boat, but since Carnival calculated the number directly from the amount of fuel consumed, I will assume it does. If the Valor traveled approximately 1800 miles (2900 km) round-trip for the cruise, this amounts to 956 kg CO2 for the trip, or almost one tonne.

However, burning diesel does emit other greenhouse gases which are not incorporated into the 0.33 kg CO2/ALB-km because the amounts emitted are small in comparison to the amount of CO2 emitted. However, from a global warming perspective these emissions are indeed significant, since their impact can be hundred of times that of CO2 alone. The same Carnival Environmental Management Report indicates emissions of 2.3 kg SOx/ALBD and 3.5 kg NOx/ALBD (ALBD = Available Lower Berth Day). For a 5 day cruise with 100 year Global Warming Potentials of 32 for Sox and 282 for NOx, this adds another 5294 kg CO2eq for the entire trip, or 5.5 times the impact of CO2 alone.

In sum, the impact of moving the boat to Mexico and back alone is 6.25 tonnes CO2eq, well exceeding the estimate from the first method. Even with an estimated 23% reduction in carbon intensity between 2008 and 2015 (again estimated from the graph in the 2015 Sustainability Report) to account for presumably increasing efficiency, this number is still at 4.8 tonnes, again well above the result from the first method.


Essentially, three different approaches yielded three different estimates for the carbon footprint associated with my spring break cruise:

  • Carbon calculator: 1.1 tonnes (components included are unclear)
  • 2015 Sustainability Report: 0.8 tonnes (scope 1 and 2)
  • 2008 Environmental Management Report: 4.8 tonnes (fuel only)

I’ll need to look more into these to assess which is the most accurate, but for now, it’s clear that the cruise had a significant impact on my carbon footprint.

New Dance Shoes

Fortunately, I recently had way too much fun at another west coast swing competition: 5280 Westival in Denver, Colorado. Unfortunately, my dance shoes are quickly reaching the end of their useful lives, and I may well need to purchase a new pair in the near future. So this week, I decided to do my due diligence and research the environmental footprint of one of the two styles of shoes I might purchase: boots. Specifically, I’m going to examine the Urban Premiere boots from Sway’D, shown below.


Image source: Sway’D shoes

SwayD is a major supplier of dance footwear for swing, and they often have a booth to display and sell their products at compeitions. The mission and values stated on their website does briefly touch on sustainability – “We weave a global community web, and we maintain positive roles in all the communities we touch through sustainability, empathy, tolerance, and love” – but as typical of these website, lacks any sort of detail.

From a brief Google search, it appears that the most research has been done into the carbon footprint of running shoes. One MIT study found that a typical pair of running shoes generates 14 +/- 2.7 kg CO2eq of carbon emissions. The study broke the total impact into five stages: materials, manufacturing (in China), use, end-of-life, and transport. The material processing and manufacturing processes account for 97% of these emissions, since running shoes are made of synthetic materials (lower material embodied carbon) that go through many manufacturing processes such as foaming and injection molding (relatively energy intensive).

However, the study notes that if the shoe were made of a natural material such as leather, the embodied carbon in the material would be much more significant. Since dance boots inevitably incorporate leather into the soles (it is much better and safer for dancing), I will attempt to modify this analysis accordingly. Since I know very little about the other four processes for the boots, I will assume for now that the values derived for manufacturing, use, end-of-life, and transport (total 10 kg CO2eq/pair) will be approximately the same for my boots as for the running shoes, and I will investigate the difference in materials more in-depth

The MIT study attributes 4.0 +/- 0.36 kg CO2eq per pair of athletic shoes to materials and processing, and it breaks down this impact by shoe part. My intuition suggests that my dance boots are much simpler than a pair of running shoes, since there are fewer moving parts and much less support. As far as I can tell, out of all the parts of a running shoe (shown below in this diagram from ASICS), my dance boots probably only have a sockliner, lasting, outsole, and possibly a heel counter, as well as an outer covering (which is much more extensive than a for running shoes). According to the MIT analysis, the socklining, other sole, and packaging together account for 20% of carbon emissions (0.8 kg CO2eq/pair). I will use this value as a starting point for my analysis, then examine the outsole and outer covering separately and add these emissions to derive the total.


Image source: ASICS, Anatomy of a Running Shoe

Outer covering: textile

The tag on the inside of my boot actually has a key noting the type of materials used (pictured below). Using this key to pictograms, I learned that the upper/outer covering is a textile.


I’m not a tailor, materials scientist, or other materials expert, but I believe the covering generally has two layers: a faux suede on the outside, and a synthetic foam-like polymer on the inside. I don’t want to tear apart my boots to get a super accurate measurement (and scraps were inevitably discarded as a result of manufacturing that will limit the accuracy of my measurement anyways), so to estimate the amount of material incorporated, I split the boot into several geometric shapes with the dimensions noted in the figure below: a cylinder for the leg/heel (blue), half of a cylinder for the toe (orange), a flat rectangle for the leather sole (pink), and two rectangles for the straps that wrap around the foot and leg of the boot (yellow). Note that I added 5 cm of length to each strap because I have previously trimmed the straps to a more appropriate length. The straps clearly have two layers of leather/suede; I assumed all of the other parts have one layer of faux suede on the outside and one of the synthetic material on the inside.


Artificial suede: With the measurements above, I estimate my boots have about 0.36 m2 faux leather per pair. If this can be approximated as an artificial leather made of polyurethane (about 3.7 kg CO2 per kg “pleather”, thickness approx. 1 mm, density 62 kg/m3), the artificial suede accounts for about 0.09 kg CO2 emissions per pair of boots.

Synthetic material: I estimate my boots have about 0.27 m2 of this synthetic material per pair. For now, I will assume this material is polypropylene. If the supposedly polypropylene material has a density of 946 kg/m3, the weave has a porosity (empty space) of about 45%, and the material is about 0.25 cm thick (from a measurement), this translates to about 0.35 kg of polypropylene material. This seems a bit high to me, given how light these shoes are, but I will use this number for now.

According to ecotextiles, polypropylene requires about 115 MJ/kg to manufacture the fiber, and 5,000 kcal/m of thermal energy and 0.5 kWh/m of electrical energy to weave the fibers into fabric. Since I don’t know the details of how all of this energy is generated, I will treat all of this energy as electricity and assume a general emission factor of 0.88 kg CO2eq/kWh (for the Chinese electric power generation grid mix).

With these assumptions, the synthetic material represents about 2.5 kg CO2 emissions per pair of boots.

Outsole: leather

The same pictogram indicates that the outsole of my boots are leather. A life cycle analysis of the carbon footprint of leather can be difficult, especially there has been some question if the impacts of raising the animals should be included, since leather is a co-product of milk and meat production. While there is not yet a standard methodology to calculate emissions associated with the leather industry, one study gives guidance that following ISO rules for LCA analysis, leather LCA should include processes from the slaughterhouse to the exit gate of the tannery (i.e. agriculture and animal farming are excluded). This actually makes a significant difference, since one estimate specific to the auto industry suggests that as much as 85% of the total carbon footprint of leather would be produced during cattle breeding and agricultural processes, were these included in the analysis. Similarly, another study of light leather production estimates about 53% of the carbon footprint would be attributed to agriculture and breeding, were these included in the analysis. For this analysis, I have decided to exclude the carbon attributed to agriculture and breeding.

One study analyzes the life cycle carbon footprint for producing light leather from sheep and goats, which is generally intended for manufacturing clothing and footwear. It estimated a total carbon footprint of 5.81 kg CO2eq/m2 leather.

I estimated the area of leather required to manufacture one pair of boots by actually measuring my current pair of black Sway’D Urban Premiere Boots. If I measure the sole of my shoe as a rectangle (not completely unreasonable, since scraps were likely generated in the manufacturing process), there’s about 0.016 m2 of leather in one shoe, or 0.032 m2 per pair. This represents about 0.19 kg CO2 per pair of boots.


With all of these factors combined, the total footprint looks like this:

  • Manufacturing, use, end-of-life, transport: 10 kg
  • Socklining, sole (other), packaging: 0.8 kg
  • Outer lining (artificial suede and polypropylene textile): 2.6 kg
  • Outsole (leather): 0.19 kg
  • TOTAL: 13.58 kg CO2

Carbon Impacts of West Coast Swing Socials

West coast swing dancing is a huge part of my life, and I usually attend at least one dance social a week. To quantify the impacts of social dance on my environmental footprint and to follow up on my January 15 post about ASDC preparation, I decided to examine the impacts of social dancing, specifically regarding attending the AggieWesties social at Texas A&M in College Station last night.

So that I don’t double-count energy usage over the course of the year, I decided to look specifically at how attending a dance social increases (or decreases) my environmental impact when compared to a base case: working, watching a movie, browsing the internet, etc. on my laptop in my room on campus (let’s be real, this is probably where I would be if I weren’t dancing). I considered separately three main ways in which dance socials impact my energy consumption: building conditioning, direct electricity use, and transportation.

Building Conditioning

This was easily the trickiest of the three categories, since I have no real information on the types of lights and sound equipment used or about the building air conditioning equipment either at Rice or Texas A&M. Since my actions don’t affect environmental loads, I considered only internal thermal loads.

First, I estimated air conditioning loads from occupant heat gain (850 Btu/h/person for moderate dancing at the social, and 450 Btu/h/person for sedentary activity at home). I then estimated how much cooling would be required to offset heat from power consumption for the devices I would be using (lights and speakers at the social, laptop and desk lamp at home); I assumed that all of the energy used to power these devices would eventually be transferred to the space, and I divided the energy consumption at the social by the number of people who attended. In sum, internal loads at the social were 940 Btu/h/person, while internal loads at home were 670 Btu/h/person.

In gross estimation, I assumed that the HVAC systems in both locations consumed about 1.1 kWh electricity per ton of cooling required. Since I assumed equivalent building HVAC efficiencies, I can use subtraction to calculate that by attending the social, I contributed 270 Btu/h/ (0.02 tons cooling) more heat to the internal load of the A&M recreation center than I would have contributed to the internal load of Martel College at Rice University. This increase in internal load then equates to 0.11 kWh of electricity over the 4.5 hour social dance. Using the weighted average carbon footprint of ERCOT calculated previously, this is 0.05 kgCO2eq.

Direct Electricity Use

From the same equipment assumptions discussed previously (lights and speakers at the social divided among the number of dancers, laptop and desk lamp at home), I found that I actually directly consumed 0.22 kWh electricity LESS at the social than I would have at home. Thus, my carbon impact from attending the social related to direct electricity use was actually -0.1 kgCO2eq.


The social was in College Station, Texas, and I drove 195 miles round trip to attend. Assuming my 2001 Honda CRV gets about 20 mpg, and splitting emissions among the three people in my car, this equates to 28 kgCO2eq.


The sum total of the carbon emissions due to energy use for the social were essentially 28 kgCO2eq, and this results one key result regarding the carbon impacts of dance socials: I think building energy use can be justifiably ignored in future calculations for the impacts of dance socials. In terms of electricity use, the increase in internal load on the building’s HVAC system was essentially offset by the decrease in direct electricity use. Even though I made a large number of gross assumptions in the calculation, they were at least of the same approximate order of magnitude. In addition, the net impact of electricity use paled in comparison to the impact of traveling to the social. Thus, to analyze socials (and competitions such as ASDC) in the future, I will consider only travel for primary and secondary carbon emissions.

Peppermint Tea with Honey

This week, I have unfortunately been feeling a little under the weather with a self-diagnosed common cold. The seemingly massive quantities of DayQuil, tea, and Kleenexes I have consumed over the past few days have begged the question: what are the environmental impacts of the common cold? To begin to answer that question, I will examine the impacts of tea.

Previous research by Nigel Melican suggests that tea’s carbon footprint can vary from 200 g CO2 to -6 g CO2 per cup of tea, depending on how it is grown, processed, shipped, packaged, brewed, and discarded. I will not go as in depth in my analysis here as Melican did in his, but I hope to examine at least a few key components of the process.

Since I discovered that mint tea with honey works wonders on a sore throat, I’ve been slowing sipping the beverage from a Keurig Stainless Steel Travel Mug (14 oz) for the past few days. The mug keeps my tea warm for several hours, so I estimate I’ve had about 2 full mugs worth of tea each day for the past four days, or 8 mugs (112 oz) total. To examine the environmental impacts of tea, consider each of the following sections separately: cleaning and transporting the water, heating the water, manufacturing and transporting the tea bag and honey, disposing of the tea bag, and washing my Keurig Travel Mug.

Water delivery: 1.6 g CO2eq/14 oz

Moving and treating water in our municipal supply system certainly requires energy, so there is embedded carbon associated with the energy required to deliver water to campus for my tea. Note that the energy intensity of these processes range considerably based on the systems used and their efficiencies. I am not yet familiar with the water treatment system in Houston, so I will use a worst case scenario (high end estimates) for combined water supply and conveyance, treatment, and distribution: 31,200 kWh/MG. I won’t directly include the energy associated with wastewater collection, treatment, and discharge, which would add another 5,000 kWh/MG to the total energy intensity, because I am unsure of what percentage of the tea will actually pass as wastewater. Overestimating energy intensity on the delivery side will likely account for this regardless.

With these assumptions, 14 oz of water requires 0.0034 kWh of electricity to deliver the water. At 0.47 kg CO2eq/kWh consumed, this is 1.6 g CO2eq.

Heating the water: 14 g CO2eq/14 oz

For the most part, I get most of the hot water for my tea from the hot water tap on the side of the coffee maker in the servery, a Bunn Model ITCB-DV. According to the installation manual for the machine, the recommended water temperature at sea level is 200°F (93.3°C) – just below the boiling point of water. Also, the manual specifies to connect the brewer to a cold water system. For now, I’ll assume that the water comes in at about 60°F (15.6°C). This is somewhat based on an anecdote that cold tap water in Milwaukee is 49.6°F (9.8°C), and Houston is generally warmer than Milwaukee, and the maximum temperature considered safe in Denmark is 77°F (25°C).

The coffee maker uses energy in two main ways: heating water to the appropriate temperature, and keeping water hot in the storage tank (offsetting losses from conduction through the walls of the tank). To calculate the energy required to heat the water for my tea, I’ll assume that enough people use the hot water that it doesn’t sit in the holding tank for an extended period of time. In this scenario, most of the energy required to deliver hot water to my cup comes from heating the water from supply temperature to 200°F. From Q=mc(T2-T1), heating 14 oz (m=237 g) of water (c=4.184 J/g/°C) from T1=15.6°C to T2=93.3°C requires 77 kJ of energy, or 0.0214 kWh of electricity. This is equivalent to 195 Wh/gal.

The brewer in the servery is not Energy-Start Certified, as far as I could tell. However, for reference, Energy Star requires that heavily used commercial coffee makers consume at most 280 Wh/gal while brewing (and thus heating water). If the servery brewer did consume energy at 280 Wh/gal, it would be about 70% efficient.

Since I don’t have specific information on the efficiency of the brewer, I will assume that it does consume energy at the maximum Energy Star rate: 280 Wh/gal. If electricity in ERCOT has a weighted average carbon footprint of 0.47 kg CO2eq/kWh consumed, then one 14 oz serving of hot water for tea is equivalent to 14 g CO2eq.

Tea bag and honey: 18.3 g CO2eq/14 oz serving

Based on this life cycle analysis for honey, I estimate that the honey I add to my tea has a carbon intensity of about 0.7 kg CO2eq/kg honey, including production, processing, transportation, packaging, etc. Assuming I add about 9 g of honey to one 14 oz serving of tea, this contributes 6.3 g CO2eq to the carbon footprint.

The largest component of the impacts here are actually the teabag; the servery provides tea in tea bags, which has ten times the footprint of loose leaf tea. Most of the difference comes from the elaborate packaging associated with tea bags. For a very rough estimation, consider this estimate that the carbon footprint of plastic is 6 kg CO2eq/kg plastic. A tea bag with 2 g of plastic (a rough estimate) would then have 12 g CO2eq of embedded carbon.

The total footprint for the tea bag and honey is 18.3 g CO2eq/14 oz serving. For this analysis, I’ll assume that the footprint of producing the tea itself if fairly small, and I will look further into this assumption at a later date.

Waste disposal: 1.65 g CO2eq/14 oz serving

Unfortunately, I have no way of composting at my university, so I tend to throw my used tea bags in the garbage. Emissions resulting from landfilling the tea bag are complicated, encompassing methane emissions from anaerobic decomposition, CO2 emissions from transportation and landfilling equipment, biogenic carbon stored in the landfill, and CO2 emissions avoided by implementing landfill gas-to-energy projects. When all of these factors are combined, food waste has a net emission factor of 0.71 MTCO2eq/short ton food waste, and most plastics have 0.04 MTCO2eq/short ton plastic. Estimating 2 g of tea and 2 g of plastics in each tea bag gives a total of 1.65 g CO2eq per tea bag due to landfilling.

Washing the Keurig Travel Mug: 147 g CO2eq/14 oz

Since I don’t have a dishwasher, I was my mug by hand; per the instructions from Keurig, I try to wash it after every use. Estimating that I use about 1 gallon of water per wash, with the energy and carbon intensity estimates used earlier, this gallon represents about 147 g CO2eq.


Here are the totals in summary:

  • Water delivery: 1.6 g CO2eq/14 oz serving
  • Water heating: 14 g CO2eq/14 oz serving
  • Tea bag and honey: 12 g CO2eq/14 oz serving
  • Waste disposal: 1.65 g CO2eq/14 oz serving
  • Mug washing: 147 g CO2eq/14 oz serving
  • TOTAL: 182 g CO2eq/14 oz serving

The total carbon footprint of each mug of tea I drank this week was about 182 g CO2eq, which is within the range suggested by Nigel Melican. Mug washing is clearly the largest contributor to the carbon impacts (as illustrated in the graph below), suggesting that perhaps I should be more efficient with my water use when washing my Keurig mug.


Super Bowl LI

This weekend, thousands of people have arrived in Houston to attend one of the biggest national events of the year: the Super Bowl. Like most big sporting events, the Super Bowl inevitably has a large environmental impact – consider the millions of passenger-miles fans fly and drive to attend, the massive quantities of food and beverages consumed, the similarly massive quantities of waste sent to landfills and recycling centers, the electricity powering lights and air conditioning in the stadium, even the resources used to film the commercials and run television broadcasting equipment, just to name a few consumptive activities.

One estimate pegged the total carbon dioxide emissions from the 2010 Super Bowl in Miami at 310,000 lbs. The site gave no justification or references for this number, and my intuition suggests it might be an underestimate, but it still serves as an eye-opening metric for the true impact of the event. This year, NRG Energy is purchasing Renewable Energy Certificates to ensure that all of the energy supplying NRG Stadium and the George R. Brown Convention Center for the event comes from clean sources, an action which may begin to make a dent in the huge environmental impacts of the event.

However, I want to examine the event on a much smaller scale: my own personal impact due to the Super Bowl. Since the event itself is far out of my influence, and it was going to happen whether or not I watched (and let’s be real, the probability of me watching any of the actual football game is close to zero), I won’t include any of the impacts of the event as a whole (those listed at the beginning of the post). Instead, I’ll focus on my direct actions during the weekend that were related to the Super Bowl: transportation, watching the game, and eating game-day food.

Transportation: On Saturday night, we took the light rail downtown to explore Super Bowl festivities at Discovery Green. At an average of 0.36 lbs CO2 per passenger-mile and a round-trip distance of 6.6 miles from Rice University to Central Square (the station downtown), this contributed not even 2.5 lbs CO2 to my footprint. I won’t count the carbon associated with the lights, concerts, additional security personnel, etc. downtown because (1) the event was going to happen whether or not I attended, and (2) the term “attending” is already a stretch, as we only took one lap around the green through the crowds before leaving, and didn’t even participate in any of the festivities.

Watching the game: There’s always a “watch party” in my dorm at Rice, where someone sets up the game on a projector (Panasonic PT-LB60U producing 3,200 ANSI lumens with a 220 W bulb) in the commons, set up like in the picture below. Three and a half hours of projection for the game amounts to 0.77 kWh of electricity, or 0.33 kg CO2 eq (from the average Rice electricity mix carbon weighting factor from last week). Dividing this by the approximately 100 people who came to the commons to watch, I estimate my viewing of the Super Bowl results in about 3.3 g (0.007 lbs) CO2eq emissions.


Game-day food: The servery always provides an abundance of game-day food during dinner for the Super Bowl. This year, I had a plate of fried pickles with ranch for dipping, nachos, celery sticks, and cherry tomatoes. The calculations below are rough estimates of the associated carbon emissions, which sum to just over 19 lbs CO2 eq for the meal.

  • Friend pickles = 0.03 lbs CO2 eq (~30 g, 0.21 g CO2eq/g for general vegetables at Rice, doubled to account for pickling and frying processes)
  • Ranch dressing = 18.7 lbs CO2 eq (59 kg CO2e/AUD for dressings; 1 AUD = 0.72 USD on June 1, 2016; Hidden Valley Ranch $3.50/24 oz)
  • Tortilla chips = 0.08 lbs CO2 eq (~15 g, 2 g CO2eq/g bagged potato chips, as approximation)
  • Celery sticks = 0.001 lbs CO2 eq (~15 g, 0.21 g CO2eq/g for general vegetables at Rice)
  • Cherry tomatoes = 0.35 lbs CO2eq (three ~16 g tomatoes, 3 g CO2eq/g tomato)


In sum, my total impact from transportation, watching the game, and eating game-day food is just about 22 lbs CO2eq.

Energy Use on Campus

Buildings consume a lot of energy, most of which powers mechanical equipment, lighting, and plug loads. Producing and delivering this energy has associated carbon and water impacts; thus my footpring associated with living in the dorms on campus will likely be a significant portion of my environmental footprint. This post is dedicated to quantifying the environmental impacts from living at Rice University.

However, my electricity usage is not individually metered, and I don’t pay utility bills. While I have an energy meter on the power strip that supplies most of devices (computer, phone charging, desk lamp, etc.), this represents only a fraction of my total consumption. To estimate my energy consumption on campus, a Rice sustainability professor offered numbers on the actual amount of electricity and natural gas consumed on campus in 2016. I used this data, the number of students living on campus, and estimations of the water and carbon footprints for various energy sources to estimate my footprint.

Step 1: Calculating consumption per on-campus student at Rice

To calculate how much energy each student living on the Rice campus consumes per school year, on average, I began with the total amount of energy (electricity and natural gas) purchased by Rice University in 2016. I used a series of estimates to calculate the average student consumption per academic year, as indicated below:

  • Total student consumption during academic year =
    (2016 total consumption) x (% used in dormitories and cafeterias) x (approx. % during school year)
  • Average student consumption = (Total student consumption during academic year) / (no. beds)
  • My spring 2017 consumption = 0.5 x (Average student consumption)

Step 2: Calculating carbon and water impacts of energy use

I used lifecycle CO2eq estimates for each power source from IPCC to calculate a weighted average carbon footprint for ERCOT electricity: 0.47 kg CO2eq/kWh. From last week’s investigation into water footprint calculators, I calculated a similar weighted average for the water footprint for ERCOT electricity: 0.29 gal/kWh. Most of the electricity Rice purchases comes from the general ERCOT grid, so I used these impact factors to assess this portion of my footprint.

Note that a small amount of electricity at Rice is purchased specifically from renewable sources (solar and wind), and I used impact factors associated with solar energy for this percentage: 0.045 kg CO2eq/kWh and 0.004 gal water/kWh.

Step 3: Calculating my impact

From my estimated spring 2017 electricity and natural gas consumption and approximate carbon and water footprints for various energy sources, I calculated my total carbon and water footprints from energy consumption in the dorms, January through May 2017:

  • Carbon: 1,094 kg
  • Water: 684 gal

I will use this total estimate as a starting point to estimate this portion of my footprint. From here, I will delve deeper into what activities contribute to this footprint, including HVAC, plug loads, and lighting.