Forums | Portfolio Discussions

16 September 2021, 7:01 PM

1. Biomass conversion processes and systems.

I have learned about biomass and several methods on how to convert biomass feedstocks into useful products such as biofuel, electricity, heat, food & feed, and chemicals. There are two types of biomasses i.e. woody and high moisture content biomass. And can be further categorized as 1^st, 2^nd and 3^rd generation biomass. The disadvantage of 1^st generation biomass is that they originate from food sources. While, 2^nd generation originates from non-food source, but still compete with food production for land use. Finally, the best option is 3^rd generation biomass which doesn’t compete with food such as algae. Generally, there are three methods i.e thermochemical, mechanical, and biological processes for converting biomass into products.  Unlike biological processes, the thermochemical process works better for lignocellulosic biomass to produce syngas or bio-oil.  Converting biomass to energy products such as biofuels was widely discussed in the class. Biofuel products can be in the form of solids (e.g., pellet, briquette), liquids (e.g., bio-oil, bioethanol, green diesel), or gases (e.g., biogas, biomethane, and synthesis gas). The two major types of thermochemical processes are gasification and pyrolysis. Gasification is the thermal decomposition of biomass into combustible gases by using gasifier reactors to produce syngas (mainly H₂, CO, CH₄).  While pyrolysis is the process of converting biomass under the absence of oxygen to syngas, charcoal and bio-oil by using pyrolysis reactors. There are several types of gasifiers, among them are a fixed bed, a bubbling fluidized bed, an entrained flow gasifier etc.  Similarly, there are several types of pyrolysis reactors such as slow, fast, flash etc. However, the presence of contaminants in the products has posed significant challenges in terms of both technical and commercial aspects. These contaminants, such as sulfur, metal, ammonia, and chloride, must be treated prior to subsequent process as it will damage the catalyst.

In the second part of the class, we have been exposed to oxygenated liquid fuel and biogas production as well as the biorefineries concept. Unlike biodiesel where there are a lot of setbacks, oxygenated biofuel such as tailor-made green diesel can overcome some of the quality problems and potential to replace petrol diesel. But currently, cost prohibitive to produce.  Another interesting topic is converting biomass into biogas and biofertilizers via anaerobic digestion. However, unlike woody biomass, high moisture biomass feedstock such as POME, EFB, food waste etc. which is currently underutilized and problematic in the sense of creating malodor, water pollution, etc. is not wisely managed. Biogas then can be turned to electricity and heat or upgraded to bio-natural gas biomethane as a substitute for natural gas.  Unlike biodiesel or bioethanol, biomethane is more versatile as it can be used as fuel in both diesel and gasoline engines with minor modification. In the class, we have been exposed to several types of anaerobic digestion systems and anaerobic digesters.  Finally, we have been exposed to the biorefinery concept which guides and enables monetization of biomass to support the circular economy and the concept of biorefineries. A biorefinery is a refinery that converts biomass to bioenergy and other useful byproducts (such as chemicals) and the International Energy Agency (IEA) Task 42 has published the guideline for classification and criteria. Developing the Biorefinery Complexity Profile (BFP)/Biorefinery Complexity Index (BFI) is indeed very challenging.

2. Analysis and Evaluation

There are several ways to improve efficient usage and management of energy. It can be done through energy conservation, energy efficiency, or substitute with renewable energy. For instance, let look at the rubber industry which requires both electricity and heat for their process. Through efficient use of fuel, for instance using co-generation technology such as combined heat and power (CHP), industries would need fewer resources to satisfy the energy demand, reducing dependence on electricity from the grid, and opportunities to reduce penalty due to maximum electricity demand.  By using the heat output from the electricity production for heating or industrial applications, CHP plants generally convert 80% -90% of the fuel source into useful energy. CHP plants also reduce transmission and distribution losses (TDL) because they are sited near the end user. Thus, the saving and reduction of GHG are in turn, can improve profitability and sustainability.

3. Suggestion

Manufacturing sectors consume a significant amount of thermal energy for the heating process. These sectors are extremely reliant on fossil fuels. There is room for improvement. For instant, the rubber glove industry is dependent on natural gas for heating and drying its products. It was reported that fuel contributed 9% in overall production cost. Natural gas can be partially substituted by renewable energy i.e biogas. The production of rubber gloves results in generating a large amount of wastewater. Currently, most of rubber glove manufacturers are using aerobic treatment to treat their wastewater.  This process requires external energy (electricity) to supply oxygen and to break down the organic matter that presence in the wastewater. Alternatively, the wastewater can be pre-treated in the anaerobic process to generate and supply biogas to the process area. By using an anaerobic process, the electricity cost for supplying oxygen can be reduced.  The combinations of anaerobic and aerobic treatment processes are quite common in a waste treatment plant to achieve the complete treatment of wastewater. This approach leads to financial and environmental benefits from the reduction of operational costs associated with energy consumption and waste disposal, and renewable energy generation. However, this improvement requires some capital investment for the installation of an anaerobic treatment system and associated equipment. Therefore, a detailed energy audit needs to be carried out to establish and quantify the cost and potential saving.

4. Reflection

The Biorefinery Concept approach is an interesting topic to me. I found out that it is a useful tool to develop the biomass-based industry as it enables monetization of biomass especially from oil palm industry and municipal solid waste to support the circular economy. Many publications have discussed about biorefinery concept for palm oil waste i.e empty fruit bunches (EFB) and palm oil mill effluent (POME) to produce high value biochemicals, bioenergy, algae etc.  However, the current approaches are too focus on “technology push” rather than “market pull”.  I believe it is the right time now to repurpose the EFB and revisit the approaches. In my opinion “technology push” driven biorefinery concept may not be workable for the development of biomass refinery projects in our country