Maximising yields

HVO and SAF have led headlines in recent years, fostering a boom in renewable fuels reminiscent of the biodiesel boom of the early 2000s.
In many ways, the biodiesel and ethanol industries paved a path for HVO, SAF and other next generation biofuels to find quick success.
Governmental regulations, subsidies and incentives have provided a crucial driving force for biofuels producers to develop new projects and find ways to increase capacities. The increased focus on HVO and SAF has put pressure on biodiesel producers as they compete for the same feedstocks.
In certain regions, however, biodiesel has maintained a stronghold. In Brazil, for example, biodiesel is a very strong market. Increases in blending mandates have stimulated investment in new plants and significant capacity expansion.
As the third largest producer of biodiesel globally, and with double-digit production increases in recent years, there is an upward trajectory in the industry with significant momentum to continue expanding biodiesel production.
This combination of factors seems to have overshadowed investment in HVO and SAF in this region. Biodiesel technology has evolved significantly over the last two decades as fuel standards have tightened.
As a result, fuel quality has improved and technological advancements have increased yields and reduced operating costs.
More and more producers are adopting waste and poor-quality feedstocks to supply these plants.
These alternative feedstocks present a significant opportunity for the renewable fuel industry but this also requires special processing considerations for biodiesel in particular.
It’s all about fatty acids
Base-catalysed transesterification is the workhorse of the biodiesel industry.
While there are a handful of other technologies that produce methyl esters, none have reached the scale of transesterification.
With the increased use of waste and poor-quality feedstocks, the content of free fatty acids (FFA) also tends to increase, which is something of an Achilles’ heel for transesterification.
Fatty acids (whether “free” or bound to glycerol) are the precursors to biodiesel and renewable diesel (HVO) molecules, so there is some irony in the fact that FFA are a contaminant to base catalysed transesterification.
If the feedstocks are not properly pretreated to significantly reduce FFA, the basic catalyst (typically sodium methylate) will react with the FFA to create soap.
The soap must then be removed, or, more often, converted back to FFA by reacting with acid the process and increases operating costs, but the FFA remains with the finished biodiesel and risks exceeding the TAN specification of the finished product.
All is not lost, however, as there are several solutions to handle the FFA. Prior to transesterification, the FFA can be converted to methyl esters via acid-catalysed esterification. This utilises strong acid, which requires costly corrosion-resistant equipment and complicates handling due to safety hazards.
Esterification is most practical when the FFA is in concentrated form. Higher concentrations of FFA reduce the volume of material to be reacted, reducing the size requirements for equipment. FFA can also be converted back to a glyceride form through the process of glycerolysis, which essentially reassembles FFA and glycerol back into mono-, di- and/ or triglycerides.
This is an effective means to reduce FFA in a feed stream, but it also creates heavy energy demand.
Spotlight on enzymes
In the last decade or so, enzymes have made significant advances in the oils and fats industry and have become a respected alternative for catalysing reactions in biofuel production. Enzymes can be used to esterify FFA into methyl esters, with good yields and attractive economics.
These processes operate at low temperature and pressure, which minimises equipment cost and eliminates the need for highly corrosive acids. There are several approaches to using enzymes, such as converting the FFA in-situ.
This saves the hassle (and additional yield losses) of upstream FFA separation from the glyceride feedstock.
The required equipment is simple: atmospheric-pressure reactors and gravity-based phase separation vessels can get the job done. In direct comparison to acid-catalysed esterification, enzymes also process highly concentrated FFA streams.
Clearing it up
Tighter quality standards are initially a disruption because they force producers to make process improvements. In the long run, however, this establishes higher-quality standards that strengthen the credibility of biodiesel as a replacement for petroleum-based diesel.
Wider adoption of higher biodiesel blends will take time as markets adjust to meet the intersection of regulatory fuel specifications and acceptance by engine manufacturers. However, many producers are going above and beyond to create the clear and colourless distilled B100 biodiesel.
The exceedingly high quality of this next generation fuel is opening a pathway toward broader acceptance of biodiesel as a means to decarbonise heavy transport.
While a technically-minded crowd might not care about appearance, there is no denying that clear and colourless fuel evokes a sense of quality and purity. Public support is key to wider adoption and a striking visual appearance can have a significant impact on consumer perception of biodiesel.
Push to B100
There has been significant progress in demonstrating the performance of pure biodiesel in rigorous tests performed by diesel engine manufacturers. In one instance, B100 was subjected to a 2,000-hour engine test where it met or exceeded stringent performance requirements. Maritime shippers in Europe and Asia are also trialling B100 as they pursue lower emissions targets. These tests follow updated performance standards and specifications in the last year that ensure engine efficiency and reliability in this important sector.
Despite competition from newer renewable fuels like HVO and SAF, biodiesel has proven resilient due to innovations in processing technology and quality improvements.
With strong regional markets and ongoing advancements, biodiesel continues to secure its place in the renewable fuels landscape.
CPM|Crown is a global leader in biodiesel and pretreatment technologies, with numerous installations of small, medium and large capacity plants. Crown’s focus on continuous improvement and innovation has helped its customers maximise yield and minimise catalyst and energy consumption, all while adapting to tighter quality specifications. l For more information: Visit oneCPM.com