Published: 4/7/2020 12:01:24 AM
David Brooks’s “Hempcrete” article (Monitor front page, March 31) extended his laudable crusade for “carbon neutrality” for products and manufacturing processes. It is more informative than he might have intended. As always, the devil is in the details. The clear evidence is exposed in his enthusiasm for “Hempcrete” insulation, claimed to be a carbon-neutral product. It certainly is not.
Brooks notes that the hemp fibre used has already taken its own carbon from the atmosphere and stored it as woody cellulose. Good. He also notes that a special variety of hemp (available only from China, Europe, and Canada) is required for making “Hempcrete” bricks. The fallacy reveals itself. Harvesting, trucking, shipping and distribution of the foreign hemp vastly increases its carbon emission footprint. Farm machines, trucks, trains and cargo ships are among the world’s chief diesel oil burners and carbon-emitters.
The use of lime as a binder-filler in “Hempcrete” brings another contradiction, one even more damning. Lime is never carbon neutral. It is made from raw, ground limestone by applying intense heat directly into it. This heat comes from the burning of massive amounts of either coal, oil or natural gas, which releases huge volumes of carbon dioxide.
“Hempcrete” is possibly a fine, efficient and suitable product when used for insulation, but its production history belies the myth of its carbon neutrality. The coming return to our energy-starved world of nuclear energy could help attain the dream of carbon neutrality by reducing the need for fossil fuels.
GEORGE R. STEVENS