INFORM April 2025

26 • inform April 2025, Vol. 36 (4)

A relative assessment of biodiesel feedstock pretreatment technologies based on client and collaborator interviews and assessments. Results may differ, and the reader is encouraged to conduct their own analysis. Source: Novonesis. Stripping/ Deodorization Chemical Neutralization Glycerolysis Acid Esterification Eversa® Advance Typical Feedstock FFA Operating Range Up to 10 wt% Up to 2 wt% Above 20 wt% Any Up to 20 wt% Capital Costs High Low-Medium High Medium Low Total Operating Costs* Low Medium High High Low Side Reactions/ Byproducts Color reduction Distillate byproduct Antioxidants loss Soapstock Tar and color formation Polymerization Sulfur and color formation None *includes direct operating costs, lost value from yield loss, downtime associated with maintenance, and value of sidestream byproducts or cost of post processing of those.

pretreatment is capable of converting up to 20 percent FFA from any feedstock into FAME. In addition to broad feedstock flexibility, the process also lowers operating costs and capital expenses compared to the other pretreatments. It is a gentle process which uses existing equipment and byproducts from the transesterification process. And the process is robust regardless of degumming variations, because phosphorus does not negatively impact the enzymatic reaction. The process involves two main steps before transesteri fication: enzymatic esterification and alcoholic neutralization (AN). During enzymatic esterification, the feedstock is mixed with enzyme and unconverted methanol contained in the crude glycerol byproduct of the AN step. The enzyme reduces the FFA concentration to less than 1.5 weight percent. Any remaining FFA is neutralized by AN using the alkaline crude glycerin available from transesterification. The pretreatment bolts onto an existing alkaline trans esterification process and requires stirred tanks made of Main Pretreatment Stripping/ Neutralization/ Glycerolysis/ Esterification Feedstock oil Sidestreams Main AN process FFA < 2 wt% if AN FFA < 0.2 wt% if no AN

low-medium grade steel for the mild reaction to run. This and gravitational separation minimize the capital requirements for the process. In addition, it can replace an existing acid esterifi cation process using existing assets, so that only minor retrofit ting is needed. The enzyme selectively converts FFA, monoglycerides (MAG) and diglycerides (DAG) to FAME while leaving tri glycerides for alkaline transesterification. Moreover, the process operates at close to ambient temperatures and atmo spheric pressure, resulting in no side reactions, low energy consumption, and minimal environmental footprint. The AN process includes a splitting step for FFA recovery from fatty matter or olein present in the crude glycerin byprod uct. However, in this novel design, fatty acids are recycled directly back into the main process to maximize FAME yields, thereby avoiding sidestream processing by providing one sin gle robust operation. Methanol is recycled from heavy phase glycerol stemming from alkaline transesterification, providing sufficient methanol to convert around 10 weight percent FFA Alkaline Transesterification Crude Glycerin Neutralized oil FFA < 0.2 wt% Crude biodiesel product Methanol and Catalyst

Alcoholic Neutralization (AN)

Neutral crude glycerin

Alkaline crude glycerin

Methanol addition for feedstocks with FFA >10 wt%

Base catalyst

Neutralized oil FFA < 0.1 wt% Methanol

Enzyme Feedstock oil

Esterified oil FFA < 1.5 wt%

Crude biodiesel

Enzymatic Esterification

Alcoholic Neutralization (AN)

Alkaline Transesterification

Optionally recycled oil from crude glycerin treatment

Alkaline crude glycerin + Unconverted methanol

Partially- or fully neutralized Crude glycerol + soap + methanol

Crude glycerin to post treatment

An illustration of the Eversa® Advance process. Source: Novonesis.

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