A Scientific Approach to Sustainability
Kansas State University researchers have used a mass balance approach to evaluate the environmental and economic sustainability of algae biodiesel.
Sustainability is an inexact term. Companies and researchers use a variety of methods to measure and project sustainability, some of which may lack a strong scientific foundation. However, a KSU research team led by chemical engineering professor Peter Pfromm, is studying the sustainability of algae-based biodiesel using a highly scientific approach: carbon mass balance.
“The application of mass balance is a very familiar item in chemical engineering,” he says. “It’s based on the scientific principle of concentration of mass, so that mass is neither destroyed nor created in a process.”
Mass balance is addressed in each unit of operation, including the algae pond, the distillation column, the biodiesel production process, and so on. “These unit operations are then knitted together with mass and energy flows to represent the entire process,” Pfromm continues. “The idea is that mass flows into and out of an operation has balance.” When the same amount of mass enters and leaves a system, the unit is balanced. When it does not, the system is unbalanced—and therefore unsustainable.
Pfromm and his team have determined that algae biodiesel produced using CO2 sourced from fossil fuel is not environmentally sustainable in terms of carbon. This is because the CO2 coming from the fossil fuels is recycled to produce biodiesel, but still ultimately ends up in the atmosphere. In other words, it is not sequestered back into the ground to balance the unit operation associated with mining. However, algae produced using renewable CO2, such as that produced by an ethanol plant, is nearly environmentally sustainable. The only unsustainable portion of the operation is the fertilizer used to make the algae, which is sourced from natural gas.
Results of the environmental portion of the evaluation, titled “Sustainability of algae derived biomass: a mass balance approach,” has been published in a peer-reviewed journal. A follow-up study will address economic sustainability. Additional members of the team include Vincent Amanor-Boadu, agricultural economics professor, and Richard Nelson, resource specialist.