Luis F. Razon

Alternative crops for biodiesel feedstock

Biodiesel, the name popularly given to fatty acid alkyl esters, has become an attractive option for the replacement of petroleum diesel (‘petrodiesel’). While its overall impact on the greenhouse effect continues to be debated, other qualities of biodiesel are unquestioned. Biodiesel is biodegradable, generally non-toxic and has superior lubricity to petrodiesel. Overall emissions are greatly reduced. The bulk of the feedstock for its production comes from renewable resources and when biodiesel is used as a blend (up to 20%); no changes are required for existing diesel engines. However, it is still too costly and about 60–80% of the cost for biodiesel comes from the feedstock. Concerns have been raised about the propriety of using food for fuel. Proposed alternative feedstock such as Jatropha curcas address some of these concerns but have their own disadvantages. This paper is a comprehensive review of recent progress on alternative crops for feedstock and addresses the issues that may ultimately lead to their success or failure: engine performance, yield, fatty acid profile, unique minor components, unique fatty acids, toxicity and harvestability. The use of agricultural wastes, used or waste oil and microbial fats is also discussed. The conclusion is reached that a blend of oils and used oils may be the best approach for the immediate future while genetically modified plants and microalgae may provide a longer term solution.

A methodology for criticality analysis in integrated energy systems

Integrated energy systems (IES) such as polygeneration plants and bioenergy-based industrial symbiosis (BBIS) networks offer the prospect of increased efficiency and reduced carbon emissions. However, these highly-integrated systems are also characterized by the strong interdependence among component units. This interdependency results in the risk of propagation of cascading failures within such networks, where disturbances in the operation of one component results in ripple effects that affect the other units in the system. In this work, a novel criticality index is proposed to quantify the effects of a component unit’s failure to run at full capacity within an IES. This index is defined as the ratio of the fractional change in the net output to the fractional change in capacity of the component causing the failure. The component units in the entire system can then be ranked based on this index. Such risk-based information can thus be used as an important input for developing risk mitigation measures and policies. Without this information, risk management based only on network topology could result to counterintuitive results. A simple polygeneration plant and two BBIS case studies are presented to demonstrate the computation of the criticality index.

Life cycle energy and greenhouse gas profile of a process for the production of ammonium sulfate from nitrogen-fixing photosynthetic cyanobacteria.

In this paper, an alternative means for nitrogen fixation that may consume less energy and release less greenhouse gases than the Haber-Bosch process is explored. A life-cycle assessment was conducted on a process to: culture the cyanobacterium, Anabaena sp. ATCC 33047, in open ponds; harvest the biomass and exopolysaccharides and convert these to biogas; strip and convert the ammonia from the biogas residue to ammonium sulfate; dry the ammonium sulfate solution to ammonium sulfate crystals and transport the finished product. The results suggest that substantial reductions in non-renewable energy use and greenhouse gas emissions may be realized. The study opens the possibility that Haber-Bosch ammonia may be replaced with ammonia from a biomass process which simultaneously generates renewable energy. The process is intrinsically safer than the Haber-Bosch process. However, there are trade-offs in terms of land use and possibly, water.

Is nitrogen fixation (once again) “vital to the progress of civilized humanity”?

The world food supply has become dependent on synthetic fertilizer from ammonia, which comes from the Haber–Bosch process. This process consumes large amounts of fossil fuels and releases large amounts of greenhouse gases. The excessive use of synthetic fixed nitrogen fertilizers has led to severe environmental effects, but fixed nitrogen is essential to the sustainability of biofuels. Nitrogen fertilizers are also required for biotic carbon capture schemes like bioenergy with carbon capture and storage (BECCS), afforestation, and soil carbon sequestration. Ammonia has been proposed as a non-carbon emitting alternative fuel that has many advantages over hydrogen. Organic agriculture and nitrogen recovery from waste streams may only partially reduce the demand for synthetic fixed nitrogen. Social solutions like population stabilization may be the best solution for the food supply problem, but ammonia is an enabling technology for alternative fuels and carbon sequestration. Alternative processes for nitrogen fixation are very early in development. This paper offers the viewpoint that alternative means of nitrogen fixation and the wise use of fixed nitrogen need to be developed quickly.

Analyzing the disruption resilience of bioenergy parks using dynamic inoperability input–output modeling

Bioenergy parks are low-carbon industrial symbiosis networks that are comprised of biomass processing plants. However, such highly integrated energy systems are inherently vulnerable to capacity disruptions. The strong interdependencies among component plants in a bioenergy park decrease system resilience due to cascading failure effect. The consequences of such disruptions are even greater if the critical components are damaged. Resilience is defined as the ability of an energy system to withstand a disruption and subsequently recover to its normal state. In this work, a disruption resilience framework is developed to analyze the resilience of bioenergy parks against an array of capacity disruption scenarios. This framework is derived from dynamic inoperability input–output modeling previously used in economic and critical infrastructure systems. A microalgal multi-functional bioenergy system case study is presented to demonstrate the applicability of the resilience framework. The example shows that the resilience of a bioenergy park is influenced by both the recovery time of component plants and their degree of connectivity within the network; such insights can be used for planning more disruption-resilient bioenergy parks.

P-graph approach to criticality analysis in integrated bioenergy systems

The use of integrated bioenergy systems (IBS) is a prospective solution to address the emergent global demand for clean energy. The sustainability of IBS compared to stand-alone biomass processing facilities is achieved through integration of process units or component plants via their bioenergy products, by-products, wastes, and common utilities. However, such increased component interdependency makes the resulting integrated energy system vulnerable to capacity disruptions. IBS in particular are vulnerable to climate change-induced events (e.g., drought) that reduce the availability of biomass feedstocks in bioenergy production. Cascading failure due to such supply-side disruptive event is an inherent risk in IBS and may pose a barrier to the commercial-scale adoption of such systems. A previous study developed a risk-based criticality index to quantify the effect of a component’s disruption within integrated energy systems. This index is used to rank the component’s relative risk in the network based on the ripple effects of its disruption. In this work, a novel P-graph approach is proposed as an alternative methodology for criticality analysis of component units or plants in an IBS. This risk-based metric can be used for developing risk management polices to protect critical facilities, thereby increasing the robustness of IBS against disruptions. Two case studies on determining the criticality index of process units in an integrated biorefinery and component plants in a bioenergy park are used to demonstrate the effectiveness of this method.

Multi-criteria approach to assess stakeholders preferences for selection of biodiesel feedstock in Vietnam

Biodiesel has been proposed as an alternative to petroleum diesel fuel in Vietnam but Vietnam is a net importer of vegetable oil. Decision-makers face challenges in crafting a long-term policy for sustainable development of biodiesel that balances social, technological, economic and environmental aspects. The analytic hierarchy process (AHP) was applied in this study to find the most appropriate feedstock for biodiesel production in Vietnam among three possible options: jatropha oil, fish fat and waste cooking oil. The judgments of different Vietnamese stakeholders, such as academics, heads of biodiesel projects, managers in Petrovietnam Corporation, and engineers were incorporated. The stakeholders showed different preferences as reflected in the priority weights of criteria and alternatives. The priority weights of alternatives under the judgments of multiple stakeholders indicate that waste cooking oil is the most preferred feedstock to produce biodiesel in Vietnam followed by jatropha oil and fish fat.

Methyl esters (biodiesel) from Pachyrhizus erosus seed oil

ABSTRACT The search for additional or alternative feedstocks is one of the major areas of interest regarding biodiesel. In this paper the fuel properties of Pachyrhizus erosus (commonly known as yam bean or Mexican potato or jicama) seed oil methyl esters were investigated by methods prescribed in biodiesel standards and comprehensively reported. As a result of the elevated content of saturated fatty acid methyl esters, the cloud point is high, the fatty acid methyl esters obtained from P. erosus seed oil generally meet fuel property specifications in the American and European biodiesel standards ASTM (American Society for Testing and Materials) D6751 and EN 14214, respectively, including a high cetane number.

Physico-Chemical Properties of Biodiesel from Various Feedstocks

In this study, plant oils were extracted from a wide variety of seeds to evaluate their potential as possible feedstocks for biodiesel production. The extracted oils were investigated by determining acid value, free fatty acids, tocopherol concentration, iodine value, density, water content and kinematic viscosity, etc. Afterwards, biodiesel was produced through esterification in the presence of methanol by using acid catalyst followed by transesterification with alkali catalyst, particularly when the FFA content of the oil was high. The biodiesel from these feedstocks were then analyzed for their physico-chemical properties such as acid value, tocopherol, iodine value, density, water content, kinematic viscosity, pour point, cloud point, flash point, cold filter plugging point, carbon residue content, oxidation stability, methanol content, and total glycerol, etc. Correlations between biodiesel properties were subsequently evaluated and the obtained results were discussed for improved biodiesel production.

A design of experiments approach to the sensitivity analysis of the life cycle cost of biodiesel

Economic feasibility is one of the major factors that has to be considered in the decision to continue with alternative fuel development. Economic feasibility of these alternatives can be assessed through life cycle costing, which is dependent on volatile parameters such as feedstock price, operating rate, capacity, interest rate and conversion efficiency. Uncertainty analysis is necessary to determine the robustness of the life cycle cost estimates. In this study, design of experiments was demonstrated to be an effective approach to analyze the sensitivity of life cycle cost to these parameters. Furthermore, the sensitivity analysis can be done based not only on the individual effects, but also on the interactions of parameters. Data from the biodiesel program of Vietnam were used as a case study. The results show that operating cost and feedstock price have the most significant effects on biodiesel cost followed by capacity, interest rate and conversion efficiency. Interactions were observed between conversion efficiency and feedstock price; interest rate and operating rate; and feedstock price and interest rate. The regression equation obtained from sensitivity analysis shows that the cost of jatropha biodiesel is 0.72–1.02 US