3D Printing Mini-Bioreactors for Anaerobic Digestion Screening

In the recently published ‘Development of an Anaerobic Digestion Screening System Using 3D Printed Mini-Bioreactors,’ authors Spyridon Achinas and Gerrit Jan Willem Euverink employ additive manufacturing for creating devices meant to act as screening tools in bioenergy applications.

Today, anaerobic digesters are used as systems for treating waste, with bioreactors usually available in a variety of different shapes. The devices are not only used to handle waste with the help of microorganisms, but they are responsible for producing ‘high-value products’ like biogas and biofertilizers.

Internal and external dimensions of the mini-bioreactor.

Reactors may be large-scale, on the magnitude of a plant-scale reactor, or smaller. The authors explain that there is a need for reactors on the micro- or mini-scale as anaerobic digestion processes become miniaturized. During that process, sensory data can be increased—but maintained in a relatively small area—saving money and energy. Geometric integrity continues with the downsizing, which is sometimes referred to as isometric scaling—while other elements may not scale in a similar fashion (allometric).

“The results demonstrated that AD in low working volumes was feasible and efficient in terms of biogas quantity and quality. The results also established links between scale-down and process stability,” stated the authors.

40 mL bioreactor samples were 3D printed for testing anaerobic digestion (AD) as well as stability. Fabricated on an SLA 3D printer with Formlabs Clear FLGPCL02 proprietary resin, the researchers used the lowest resolution possible at 0.1mm. The sample was described as ‘sturdy and rigid,’ requiring support structures, 63mL of resin, and 8 hours of printing time.

Development of the sample included:

• Vessel design
• Vessel fabrication
• Operation test
• Baseline study

The validation step of the miniature system consists of a baseline study operating commercial bioreactors and the conceptual research with the 3D-printed mini-bioreactors.

The researchers performed a single-stage, semi-continuous process for the 400mL vessels, each offering a working volume of 300 mL. Overall, samples were developed with ‘advanced features’ due to the high resolution, allowing features like:

• Spaced and geometry-controlled baffles
• Sample ports
• Sensor inlets
• CAD-designed internal structures

Process conditions and masses of organic materials in experimental tests.

“Furthermore, the direct printing of high-quality threads allowed working under controlled back pressure,” concluded the researchers. “Indeed, the micro-bioreactor manufactured here showed a similar performance as the commercial bioreactor in biogas production from the anaerobic digestion of milk.

“The simplicity, low cost, and rapid update of 3D printing technology will enable the development of numerous applications of advanced reactor engineering in continuous-flow chemical manufacturing. The conclusions of this work justify the use of mini AD systems for high-throughput process screening to improve AD systems further. The excessive amounts of biowaste and wastewater produced in our society need to be taken care of properly. Better performing AD reactors contribute considerable to the sustainable treatment of biowaste and wastewater.

And while there is some controversy regarding how to deal with waste caused by 3D printing, this is an industry also heavily associated with upcycling, recycling, energy, and much more. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

Daily biogas production during the experimental period.