Is it Local?
This article is part of Building Climate-Positive, a project diary to build a carbon negative dwelling –exploring architecture and design solutions that address the climate crisis.
Construction is essentially complete, but this question has been sitting on my desk for more than a year now. Is it justified to import so many materials we rely on for a healthy and sustainable home? Shouldn’t we use local sources?
“Oh, so if the hemp is not local, then it’s not actually sustainable, right?”
We heard this or similar comments during several open house events, tours or talks we held during the hemp installation process. Yes, the hemp we used was not local, it was imported from Europe.
We felt pretty confident that this generalization was a misconception, and wanted to analyze AND visualize transportation emissions for a few select products. To be clear, anything that doesn’t have to travel at all, is definitely less carbon — intensive. But when it comes to freight, it is worth paying attention to the mode of transportation and where exactly things come from.
According to the MIT Climate Portal, freight transportation is responsible for 8% of global greenhouse gas emissions. While nearly three-quarters of the world’s cargo is carried by ocean-going ships, road vehicles like trucks and vans make up the majority, 62%, of freight’s emissions.
Recent supply chain disruptions have forced us to pay more attention to where stuff actually comes from and how. Producers and distributors are warning us about “18 weeks lead time” or “Many of our products are taking longer to get to us and therefore we cannot guarantee availability.”
Reliability aside, I was curious to see how transportation emissions “Gate to Site” (A4 in the Life Cycle Analysis) compare from different points of origin — and as result different modes of transportation.
And if you add up emissions from Harvest to Site (A1 - A4), can the stored carbon in some of the materials we chose make up for the long distance traveled.
Is local always better? And what is considered local?
The US Green Building Council in its version v4.1 for single family homes defines it as within 100 miles of the project site for LEED certification. It offers up to 3 points, when 50% of the following are were extracted, processed, and manufactured locally: (1) framing, (2) aggregate for concrete and foundation, (3) drywall or interior sheathing. No other building component is mentioned.
Note that to achieve LEED certification, you need a minimum of 40 points. In other words, the US Green Building Council in its current iteration of LEED does not put a lot of emphasis on embodied energy or sourcing materials locally — most likely a reflection of how difficult it is to track either.
Here is an imperfect attempt to track the hemp and lime in our project.
The hemp was harvested and processed in France by a cooperative of hemp farmers founded in the 1960s. Together with the lime binder it was shipped to our hempcrete contractor Americhanvre in Pennsylvania, and then from there to our site in Columbia County. Since the 2018 farm bill legalized hemp growing in the US, many farmers have taken to growing hemp. However, the processing of industrial hemp for use as building material is still in research phase at best. In addition hempcrete was only recently approved for residential construction in the US. Using European products with their respective fire rating certificates, was safer to ensure quality.
The journey of 15 (US) tons of hemp and lime for almost 5,000 miles does emit a significant amount, even with the majority of the trip on an ocean cargo ship. The different legs of the trip were calculated using Carbon Care, an online calculator for cargo shipping. As with everything, the numbers are approximate. We don’t know exactly every mode of transportation, but we do know, it was shipped from Marseille.
Comparing the CO emitted for the material with the embodied carbon store in it, hempcrete still comes out on top with a net carbon of negative 4240kg of CO2 equivalent for life cycle stage A1-A4.
High Performance Windows
Similar to hemp, we did not want to rely on American-made windows. Architects of high performance or passive house construction have long relied on high performance windows from Germany, Poland and Austria.
The windows for our micro homes were manufactured in Austria using sustainably forested Douglas Fir for the frames and triple-pane glass. The manufacturer did not provide an Environmental Product Declaration (EDP), but based on comparative analysis from Builders for Climate Action’s BEAM Estimator European windows have on average a lower embodied energy than American produced windows. Some of this difference is likely related to the energy source used during processing. We asked our distributor about the exact journey our windows took and used again CarbonCare to translate this into kgCO2e.
A hypothetical journey from an American window manufacturer for the same size windows with a by truck would likely be just as carbon-intensive while traveling a quarter of the distance. (Note: The carbon intensity can be lower, if a portion of this journey happens via rail. UPS, FedEX and the US Postal Service all use intermodal systems, so a portion of the journey might be by rail. Trains are four times more efficient than trucks, moving one ton of freight 470 miles on just a single gallon of diesel fuel according to the US Department of Transportation.)
The US Department of Energy estimates that by 2035, it will be cheaper to buy, own, and operate all electric powered trucks than gasoline and diesel trucks. The same year by which it hopes to have the entire electric grid decarbonized. But for the foreseeable future, what is “actually sustainable” when it comes to transportation emissions will continue to be hard to track for many products.
There can be good reasons for using materials and building components that travel long distances to their site. The mode of transportation matters more than the distance.
But also seeing how much architects wanting to use healthy and high performance materials rely on European products, it should be a wake-up call for growing a local industry for the same products.
Can we encourage hemp growers to invest in processing infrastructure to produce healthy low-carbon building materials locally? Can we change building codes to encourage the building with locally farmed materials?
