The fluctuation in the price of petroleum-based chemicals and polymers has increased the impetus to seek alternative renewable biomass resources. The long term driving force is to provide cheaper chemicals and lower polymer prices. The short term objective, however, is to develop these alternative resources in preparation for the day when the limited petrochemical resources become scarce. The key factors in this search are the processes and catalysts ^[1]. The resources will be most likely based on plants with rich polysaccharide content. While the obvious choice is soft fruits, there are many crops yielding much higher saccharides than fructose. Cereal crops (e.g. corn), potato, sugar cane, and sugar beet are traditional sources of ethanol, which is also a primary source for several industrial chemicals. While fruits, cereals and root vegetables can be used for industrial purposes, facing competition from food demands.

The richest biomass resource on Earth is lignocellulose. The search for lignocellulose utilization has led to the examination of available catalyst technologies that are not necessarily based on man-made catalysts. Catalysts such as bacteria, fungi, enzymes and algae are now being developed specifically for target chemicals. Genetic modification is also playing a vital role in these searches. In the following, the latest developments in these catalyst systems worldwide are reviewed.

Bacteria were the first life form on Earth and are more abundant than any other living organisms. Their sizes vary between 0.5 to 5 μm. Some are visible to the naked eye and can be up to 0.30 mm in length ^[2]. Carbon metabolism is either heterophobic (when organic compounds are used as carbon sources) or autotrophic (when cellular carbon is obtained by reacting with carbon dioxide). Under anaerobic conditions, the bacteria uses inorganic substances such as nitrates, sulphates or CO₂ as electron acceptors. In the absence of these electron acceptors, chemotrophs make the electrons themselves.

Bacteria convert substrates to oxidized intermediates to form fermentation products such as ethanol, lactates, hydrogen and butyric acid. Fermentation takes place and as a result the energy content of the substrate is higher than that of the products. These processes interest us in the search for bacteria as catalysts for the production of the monomers of biomass-based polymers and other chemicals.

At present, the following processes have been successfully achieved: (1) production of ethylene and propylene from fermentation of polysaccharides; (2) manufacture of a mixture of acetone (30%), ethanol (10%) and butanol (60%) from fermentation of corn starch; (3) production of succinic acid using bacteria; (4) production of sucrose from glycerol, a byproduct in the manufacture of biodiesel fuel, and (5) production of butadiene from a variety of sources such as molasses, sugarcane juice, sugar, and wood waste. Furthermore, much research & development (R&D) resources are dedicated to modify bacteria to produce modified enzymes.

PetroAlgae, Inc. at Melburne, FL, USA was the first company to set up for developing alternative fuels and petrochemicals from algae. Algae Research Laboratory at Research Institute of Petroleum Processing (RIPP), Sinopec Corp. has also been working in this area in Beijing since 2010. PetroAlgae expects to be the first renewable energy company to achieve the commercialization of drop-in replacements of fossil fuels. The key PetroAlgae technology includes large open bioreactors, access to over 150 micro-crop strains, and the understanding and control of growth fundamentals. The process overview is shown in Fig. 1. Fig. 2 shows the flow chart of the PetroAlgae process.

Fig. 1. Overview of the PetroAlgae process.

Fig. 2. Flowchart of the PetroAlgae process.

The superiority of PetroAlgae technology to other uses of biomass sources is shown in Table 1. A joint research & development program between the Chinese Academy of Sciences and Sinopec Corp. was started in 2008. Fig. 3 shows the salt water for open-pond cultivation of algae at South Sea Research Institute from the laboratory scale to a pond of 1200 m². Figs. 4 and 5 show soft water cultivation at Wuhan Botanic Institute, and the Algae Research Laboratory at RIPP, Sinopec Corp., respectively.

Table 1 Biomass yield comparison. Biomass source Biomass yield (MT/ha/yr) Soy 1–2.5 Rapeseed 3 Palm Oil 19 Switch grass 15 Alfalfa 3–8 Jatropha 7.5–10 Other Micro-crop Companies 2–50 PetroAlgae 80–100

Table 1 Biomass yield comparison.

Fig. 3. Open-pond cultivation of algae in salt water at South Sea Research Institute.

Fig. 4. Soft water cultivation at Wuhan Botanic Institute.

Fig. 5. Algae Research Laboratory at RIPP, Sinopec Corp.

It is expected that due to the abundant supply of lignocellulose, the research and development of new bio-catalyst systems for lignocellulose fermentation will be strengthened, which will lead to new products and new enterprises.