If you’ve ever poured maple syrup on your blueberry pancakes, rolled maple taffy in the snow or eaten a piece of maple candy, you know how delicious it is. If you’ve ever been to a sugar shack during the energy-intensive water evaporation from the sap, or if you followed the news about the multimillion-dollar Quebec maple syrup heist, you understand why the stuff is so expensive.
Despite the high price of maple syrup, researchers have turned toward maple sap as a feedstock for the production of the bioplastic polyhydroxybutyrate, or PHB. Diverting perfectly good sap from the maple syrup pipeline may sound like blaspheme to sensible Mainers, but the idea is gaining traction.
The thought is that sap would fill the void for the type of materials we have in the past sourced from petroleum. Ever fluctuating oil prices and the increasingly complicated measures we turn to in order to pump it from the ground highlight the dire situation: Oil will run out. When it does, we will need to find biomass-based alternatives for energy, fine chemical production and bulk materials.
The popular bioplastic polylactic acid, or PLA, different from PHB, is manufactured through chemical processes to link individual molecules of a biomass-sourced lactic acid derivative into long chains to form the polymeric plastic material.
Instead of processing the individual molecules into polymer chains ourselves, the technology for the production of PHB relies on microorganisms to build the plastic for us from sugar molecules, instead of lactic acid derivatives.
Much like we store excess sugar in the form of fatty tissue, these microorganisms build their reserves in the form of PHB. When exposed to an abundance of sugar, they go into storage mode, forming large deposits of PHB, which we can easily harvest.
Therefore, this technology represents a bioplastic in the truest sense of the word. Not only are the individual building blocks sourced from biomass (sugar), but we get microorganisms to build the polymer chain for us.
The microorganisms don’t take their sugar the same way we do, as a concentrated syrup painstakingly obtained from slow evaporation of more than 95 percent of the sap volume. They don’t mind a dilute, watery solution, so no time-consuming, energy-intensive and expensive evaporation required. With evaporation out of the picture, the price of the maple feedstock drops from $75 a gallon to pennies.
Because they built the polymer as a means for energy storage, they — and other organisms — also have the toolset to break it down. So not only is this polymer sourced from biological material, it is easily biodegradable, which is not always the case with bioplastics. That PLA cup or chip bag, for example, won’t break down in your backyard compost; it takes a municipal composter under very specific conditions. An even worse example is Rilsan, which, though sourced from canola oil, is not biodegradable at all.
With many bioplastics, PLA and Rilsan included, diverting resources from the food supply for the production of bulk materials represents a major concern. Should we grow corn and potatoes for PLA production or Canola for Rilsan production when they instead could be used to meet the ever increasing food demands of a growing population?
Considering the vast number of untapped maple trees in the Maine woods — and the many more in New Hampshire, Vermont, Quebec and other neighboring states and provinces — this PHB process wouldn’t need to divert sap from the trees dedicated to syrup production; it simply could tap into those already not being used.
Sure, if the technology really took off, we may see a slight increase in the price of maple syrup, but wouldn’t that be worth the steps taken to wean ourselves from petrochemical-derived, non-biodegradable plastics?
Reuben Hudson is a postdoctoral fellow in chemistry at Colby College in Waterville.