Footprint: The Environmental Impact of Thru-Hiking the PCT
By Karl Schmidt
I was hoping to make a short movie on this topic for the ADZPCTKO film festival this year but I just didn’t find the time amidst preparation and other preoccupations. I wanted to create this blog post to initiate a discussion and reflect my research and considerations.
It is understood today that we humans play a significant role in the global ecosystem; the actions of our species matter. The educated, affluent citizens of the United States have a responsibility to understand and consider the consequences of our choices. Every choice we make: such as the food we eat, the clothes we wear, what we do with our waste and the adventures we choose to take, has some environmental impact. Corresponding impacts may be healthy or unhealthy for the environment.
In planning my PCT thru-hike I was curious about the environmental impact of the endeavor. My initial impressions were that spending four to five months hiking a trail would have a lower environmental impact than the way I was living my life in the Bay Area suburbs. (Many consider my lifestyle to be environmentally friendly already.) Not long after having this thought did it seem arbitrary to me; what does it mean to have a “lower” environmental impact. No matter what, we have an environmental impact, for example, we breathe oxygen produced by plants and plankton doing photosynthesis and exhale carbon dioxide that those organisms need to grow and continue photosynthesis. What I decided to consider were the negative effects humans have on the environment, and attempt to quantitatively compare the PCT thru-hike and my at home lifestyle.
The three negative impacts I considered were: the release of carbon dioxide by burning fossil fuels, the consumption of fresh water resources, and the production of non-biodegradable waste.
---- Carbon Dioxide ----
Carbon dioxide is a greenhouse gas. A greenhouse maintains a high air temperature by allowing visible light to enter through glass and be absorbed by plants and earth but trap the infrared radiation that is emitted from the warmed earth. (Students in my high school physics class saw that a pane of glass blocked the infrared -heat- radiation from a heat lamp.) Similarly as the surface of the Earth heats up from Solar radiation and then emits heat mostly as infrared radiation, carbon dioxide molecules in the atmosphere absorb some of this heat and then re-radiate it in a random direction. Some of the heat thus remains within the atmosphere.
Water molecules in the atmosphere similarly absorb and re-emit infrared radiation. There is a balance between the heat the Earth gains on the side facing the Sun -day side- and the heat lost on the night side. We rely on the greenhouse effect to maintain a habitable nighttime temperature on Earth, however, trapping more heat maintains a higher temperature. The intensity of incident solar radiation on the day side -half the surface of the Earth- is about 1000 Watts/(meter)^2. By doubling the average concentration of carbon dioxide in the atmosphere the heat trapped adds 4 W/m^2 to the entire surface (the Sun only shines on half the planet but Earth is constantly radiating in all directions). This is equivalent to one of those old style Xmas tree or night light bulbs that you may remember gets pretty hot despite most of that radiation to be visible light. Excessive CO2 is released into the atmosphere through the combustion of fossil fuels in cars, trucks, planes, ships, stoves, furnaces, and power plants.
The release of this CO2 is often referred to as one’s “carbon footprint.” By determining my carbon footprint during five months of my suburban lifestyle I calculated what area on the Earth I was doubling the concentration of CO2 and thus adding 4 W/m^2. This method is an oversimplification, but illustrates my carbon footprint.
I combust fossil fuels to transport myself by car, use electricity, heat water and cook and heat a house. I started by looking at my monthly bill from PG&E. The PG&E website provides calculator to estimate your carbon footprint. They said mine was 7,083 lbs/year. Based on values from the EPA I estimated my own carbon footprint for the five months I’ll be hiking. Combusting gasoline produces 8.91 kg CO2/gallon. I use an average of 33 gallons per month during the summer. (This is low for most people, especially those who commute by car.) This releases, after conversion to pounds, 3242 lbs CO2. It is important to calculate this value using the kg CO2/gallon, the PG&E website asks how many miles you drive but that does ignores the efficiency of you car.
Similarly the EPA says burning natural gas releases 5.306 kg CO2/therm. My average usage is about 12 therms per month, producing 702 lbs CO2 in five months. And PG&E quotes a value of 0.559 lbs CO2/kWh of electricity consumed. I use approximately 92 kWh per month releasing 567 lbs CO2 in five months. My total carbon footprint in five months is thus 4512 lbs CO2. My yearly estimate is higher than PG&E webpage value (even excluding the fact that my electricity and natural gas consumption increase in the winter months), but they agree on the order of magnitude.
While hiking the PCT 4512 lbs of CO2 will not be released into the atmosphere and thus not contribute to the increasing greenhouse effect. It is very reasonable to have no idea what 4512 lbs of CO2 means, I didn’t. In order to make this number meaningful I asked, given that doubling the concentration of CO2 adds 4 W/m^2: in what area (m^2) does my five month carbon footprint double the concentration of CO2 and thus add 4 W/m^2?
The way I answer this question provides a sense of scale to my carbon footprint but is in not an accurate description of the way one person’s CO2 interacts with the atmosphere because I ignore the mixing mechanisms of our atmosphere.
(I will explain the method I used, see the figures for the mathematics. If you want to trust my calculation you can skip this an look at the result.)
By approximating the atmosphere as fluid in hydrostatic equilibrium, i.e. there is no motion so the pressure and density are functions of depth due to gravity. The density of the atmosphere decays exponentially with altitude. The scale height of the atmosphere is where the density drops to 1/e or ~ 1/3 the value at sea level because 2/3 of the atmosphere is below that level it is a reasonable approximation for the height of the atmosphere. This scale height, approximated using a constant temperature of 7° C and an atmosphere of nitrogen (N2), is 8500m. Yes, this is lower than the height of Mt. Everest. Did you notice it’s hard to breathe up there?
By integrating through altitude I found a sort of surface surface density which is only a product of the density at sea level and the scale height of the atmosphere. This is a nice result courtesy of the decaying exponential. I know the mass of CO2 I release in those five months so I must find out the area that contains this same amount at the average concentration, 390 parts per million (ppm). Adding my CO2 would thus double the concentration if it were contained above that ground area. Parts per million refers to the concentration, i.e. the ratio of mass of CO2 to the mass of the air. There are 390mg CO2 per kg of air, so the concentration is 3.9x10^-4. The density of air (at sea level) is the mass of air per unit volume. A substitution can be made for the mass of air in this column leaving the density related to the mass of CO2 (my carbon footprint), the concentration and the volume. The volume can be represented as a product of the ground area and the height. Here I can use the scale height of the atmosphere. So the area in which the concentration would be doubled is the area of such a column that contains the same mass at average concentration. The area is the mass of CO2 divided by the surface density and concentration.
I calculated and area of 520 m^2 or 5665 sq.ft. This is approximately the area on a football field from the goal line to the 12 yard line (I mistakenly did not divide by three on the written page, that is 35 ft from the goal line). Recall in this region due to the doubled concentration of CO2 there is an extra 4 W/m^2 or 2080 W, all the time.
During my thru hike I will NOT release this CO2 and therefore have a lower carbon footprint.
---- Water ----
Fresh, clean water is necessary for humans and other wildlife to survive. As the human population increases the demand for fresh water increases. While we only need to consume two to three liters (L) (~0.75 gal) per day to survive, we use huge quantities of water to shower, wash dishes and flush the toilet. Also the food that sustains us, and the materials we use for construction, clothing, and goods all require water to produce. I measured the amount of fresh water that I use for showering and toilet flushing for five months because this is the water that will be conserved while living on the trail.
Water conservation is a critical concern in densely populated areas. Increased demand on freshwater impacts wilderness areas and ecosystems directly. The Tuolumne River in Yosemite was damned, creating the Hetch-Hetchy reservoir to supply San Francisco with water. The aquifers in the California Central Valley have been significantly reduced to supply water for agriculture and Southern California. The Colorado River, no longer drains to the Gulf of Mexico because all the water is diverted for Las Vegas and Los Angeles. The Salmon runs along the West coast of the US are miniscule in size relative to before rivers were damned for water and power generation.
I estimated the amount of water I use for showering and flushing the toilet. My toilet uses 1.6 gallons (6 liters) per flush. Note that the eight glasses of water, 8 fl oz each, recommended each day is only half a gallon. If I flush only four times a day (Trying to observe the rule: “if it’s yellow let it mellow, if it’s brown flush it down.”) then I use 24 liters a day or 3600 liters (240 gallons) in five months (150 days). My shower flows about 12 liters per minute. I measured with a bucket and a stopwatch. My average shower lasts eight minutes, and I shower once per day on average. So showering I use 96 liters (24 gallons) per day and 14400 liters in five months (3600 gallons). Together that is 18,000 liters (3840 gallons) of drinkable water used for personal sanitation.
While this is a tremendous amount of water I have found that the biggest consumption of freshwater is hidden behind the production of everything else. A recent graphic in Sierra magazine gives the values of the amount of water required to produce certain items, the sources are linked through the website. (http://sierraclub.org/sierra/201205/grapple-water-footprint-173.aspx) For example: a cotton T-shirt requires 400 gallons to produce, one pound of wool: 101 gallons, four tires: 2072 gallons. I find the most appalling number to be the three quarts of water it takes to produce one quart of bottled water.
It is worthy to note the huge amounts of water consumed for agriculture, a reasonable use, but when I considered the amount of water I use to flush away urine (>90% water) and keep myself clean I notice that I will be conserving water while I hike the PCT. Most shocking is the tremendous amount of water needed to produce goods. We may regard this use as legitimate at times or the product worth it. Consideration must be given to the source of that water. Is that product consuming fresh water in a country where people struggle to find clean drinking water?
---- Waste ----
On a recent visit to the Marine Mammal Center in Marin, CA the tour guide explained to a class of high school environmental science students that plastics, by design, last forever. Plastic does not decompose. I’ve seen estimates that range from 2000 years to 22,000 years. It may be remarkable that we have relics such as the Parthenon but do we really want our memory to be our landfills 2,500 years from now. Single-use plastics are incompatible with ecology; they are simply waste. In the short term, plastic ends up in nature and harms wildlife or disrupts a wilderness experience.
However we are in the plastic age; plastic is part of our culture and society. In the backpacking world plastic is particularly useful due to its light weight. I am using hundreds of ziplock bags for food packaging, map packaging, and waterproofing. Also I am buying more individually wrapped food items convenient for packing and snacking and maintaining freshness. I packaged olive oil in small plastic bottles and soap in tiny plastic dropper bottles.
The 320 ziplock bags I am employing average about 0.15oz per bag. That is 48 oz or 3 lbs of plastic bags. I suspect its unlikely that where I dispose of my trash during my hike will have recycling options for the items that can be recycled. So this plastic along with my bar wrappers will end up in the landfill.
While the other sections of this writeup showed that I would have a smaller impact in terms of waste generation I think I will do worse during my thru hike than at home. I strive to use my own shopping bags, reusable containers and avoid packaged food. Honestly, I find that trash cans are so available in urban areas that I don't have a good handle on how much waste I generate. Whereas, on the trail I will be carrying my trash. I have always been intrigued by the experiment of keeping all the waste and trash we generate, by this I mean non-biodegradable waste, for a month to see the mass. Perhaps something we should all try.
------------------------------------
This discussion would not be complete without mentions of other choices made during a thru-hike such as resupply strategies and gear choices. The PCT thru hiker has two primary options for resupplying food: maildrops and local shopping. I chose a hybrid strategy for my hike where I am sending maildrops 75% of the time and shopping locally the other 25%. Food is shipped all over the country and even from others to get to our grocery stores. The maildrop option is adding more shipping distance to every item inside which has some carbon footprint. I dehydrated most of the dinners in my maildrops, and much fruit, bought from local growers around my home. Shipping this food is certainly increasing its carbon footprint, though it starts at a lower value than the items that I bought prepackaged such as cookies and bars and chocolate. Ultimately we hikers need the infrastructure for food transportation whether we buy our food at home and ship it to the trail or buy food that has already made its way to the trail towns. If the food is not from local sources near those trail towns then there is little difference in the carbon footprint of getting it there.
Much of my backpacking gear is made from synthetic materials, even my Western Mountaineering sleeping bag, made locally in San Jose, Ca is filled with goose down shipped from Europe. All of these materials require huge amount of water to produce. We hikers are consumers, but I'd like to think we buy less than the average American by spending our weekends hiking rather than at the mall. I consider the gear I purchased for this five month trip to be equivalent to whatever I would have been purchasing, I am a man of many hobbies, instead if I were not thru hiking, perhaps even less. I think overall it is important to try to be conscious of origin of the products we buy. I bought a ULA backpack partly because it was made in Utah. I respect the US laws for workers' rights, and environmental protection regarding industries. Patagonia has interesting information about environmental impacts on their website.
Thru-hiking the PCT is an environmentally friendly activity. It makes a statement about transportation: humans were built to walk. It makes a statement about materialism: we only need food, water and shelter to survive. But most importantly it inspires others to get outside, go for a hike and develop a relationship with nature so that we may see its value and preserve it. We are people of our time; making extreme, individual lifestyle choices, such as thru-hiking the PCT or living without a car, may not alter the current trend physically but serves to promote awareness and discussion of environmentalism.
Fresh, clean water is necessary for humans and other wildlife to survive. As the human population increases the demand for fresh water increases. While we only need to consume two to three liters (L) (~0.75 gal) per day to survive, we use huge quantities of water to shower, wash dishes and flush the toilet. Also the food that sustains us, and the materials we use for construction, clothing, and goods all require water to produce. I measured the amount of fresh water that I use for showering and toilet flushing for five months because this is the water that will be conserved while living on the trail.
Water conservation is a critical concern in densely populated areas. Increased demand on freshwater impacts wilderness areas and ecosystems directly. The Tuolumne River in Yosemite was damned, creating the Hetch-Hetchy reservoir to supply San Francisco with water. The aquifers in the California Central Valley have been significantly reduced to supply water for agriculture and Southern California. The Colorado River, no longer drains to the Gulf of Mexico because all the water is diverted for Las Vegas and Los Angeles. The Salmon runs along the West coast of the US are miniscule in size relative to before rivers were damned for water and power generation.
I estimated the amount of water I use for showering and flushing the toilet. My toilet uses 1.6 gallons (6 liters) per flush. Note that the eight glasses of water, 8 fl oz each, recommended each day is only half a gallon. If I flush only four times a day (Trying to observe the rule: “if it’s yellow let it mellow, if it’s brown flush it down.”) then I use 24 liters a day or 3600 liters (240 gallons) in five months (150 days). My shower flows about 12 liters per minute. I measured with a bucket and a stopwatch. My average shower lasts eight minutes, and I shower once per day on average. So showering I use 96 liters (24 gallons) per day and 14400 liters in five months (3600 gallons). Together that is 18,000 liters (3840 gallons) of drinkable water used for personal sanitation.
While this is a tremendous amount of water I have found that the biggest consumption of freshwater is hidden behind the production of everything else. A recent graphic in Sierra magazine gives the values of the amount of water required to produce certain items, the sources are linked through the website. (http://sierraclub.org/sierra/201205/grapple-water-footprint-173.aspx) For example: a cotton T-shirt requires 400 gallons to produce, one pound of wool: 101 gallons, four tires: 2072 gallons. I find the most appalling number to be the three quarts of water it takes to produce one quart of bottled water.
It is worthy to note the huge amounts of water consumed for agriculture, a reasonable use, but when I considered the amount of water I use to flush away urine (>90% water) and keep myself clean I notice that I will be conserving water while I hike the PCT. Most shocking is the tremendous amount of water needed to produce goods. We may regard this use as legitimate at times or the product worth it. Consideration must be given to the source of that water. Is that product consuming fresh water in a country where people struggle to find clean drinking water?
---- Waste ----
On a recent visit to the Marine Mammal Center in Marin, CA the tour guide explained to a class of high school environmental science students that plastics, by design, last forever. Plastic does not decompose. I’ve seen estimates that range from 2000 years to 22,000 years. It may be remarkable that we have relics such as the Parthenon but do we really want our memory to be our landfills 2,500 years from now. Single-use plastics are incompatible with ecology; they are simply waste. In the short term, plastic ends up in nature and harms wildlife or disrupts a wilderness experience.
However we are in the plastic age; plastic is part of our culture and society. In the backpacking world plastic is particularly useful due to its light weight. I am using hundreds of ziplock bags for food packaging, map packaging, and waterproofing. Also I am buying more individually wrapped food items convenient for packing and snacking and maintaining freshness. I packaged olive oil in small plastic bottles and soap in tiny plastic dropper bottles.
The 320 ziplock bags I am employing average about 0.15oz per bag. That is 48 oz or 3 lbs of plastic bags. I suspect its unlikely that where I dispose of my trash during my hike will have recycling options for the items that can be recycled. So this plastic along with my bar wrappers will end up in the landfill.
While the other sections of this writeup showed that I would have a smaller impact in terms of waste generation I think I will do worse during my thru hike than at home. I strive to use my own shopping bags, reusable containers and avoid packaged food. Honestly, I find that trash cans are so available in urban areas that I don't have a good handle on how much waste I generate. Whereas, on the trail I will be carrying my trash. I have always been intrigued by the experiment of keeping all the waste and trash we generate, by this I mean non-biodegradable waste, for a month to see the mass. Perhaps something we should all try.
------------------------------------
This discussion would not be complete without mentions of other choices made during a thru-hike such as resupply strategies and gear choices. The PCT thru hiker has two primary options for resupplying food: maildrops and local shopping. I chose a hybrid strategy for my hike where I am sending maildrops 75% of the time and shopping locally the other 25%. Food is shipped all over the country and even from others to get to our grocery stores. The maildrop option is adding more shipping distance to every item inside which has some carbon footprint. I dehydrated most of the dinners in my maildrops, and much fruit, bought from local growers around my home. Shipping this food is certainly increasing its carbon footprint, though it starts at a lower value than the items that I bought prepackaged such as cookies and bars and chocolate. Ultimately we hikers need the infrastructure for food transportation whether we buy our food at home and ship it to the trail or buy food that has already made its way to the trail towns. If the food is not from local sources near those trail towns then there is little difference in the carbon footprint of getting it there.
Much of my backpacking gear is made from synthetic materials, even my Western Mountaineering sleeping bag, made locally in San Jose, Ca is filled with goose down shipped from Europe. All of these materials require huge amount of water to produce. We hikers are consumers, but I'd like to think we buy less than the average American by spending our weekends hiking rather than at the mall. I consider the gear I purchased for this five month trip to be equivalent to whatever I would have been purchasing, I am a man of many hobbies, instead if I were not thru hiking, perhaps even less. I think overall it is important to try to be conscious of origin of the products we buy. I bought a ULA backpack partly because it was made in Utah. I respect the US laws for workers' rights, and environmental protection regarding industries. Patagonia has interesting information about environmental impacts on their website.
Thru-hiking the PCT is an environmentally friendly activity. It makes a statement about transportation: humans were built to walk. It makes a statement about materialism: we only need food, water and shelter to survive. But most importantly it inspires others to get outside, go for a hike and develop a relationship with nature so that we may see its value and preserve it. We are people of our time; making extreme, individual lifestyle choices, such as thru-hiking the PCT or living without a car, may not alter the current trend physically but serves to promote awareness and discussion of environmentalism.