Biofuels

Introduction

Biofuels have considered as an energy source with high potential to address problems in several aspects, such as the ciris of climate change, environmental degradation, energy supply and security. The use of biofuels largely depends on the potential of available of different feedstocks. However, biofuels havs some common features that they are all non-toxic and biodegradable, and they can reduce greenhouse gas(GHG) emissions. Recent studies from Soil and Tillage Research show that replacing fossil energy with renewable energy, like biofuels, is an important way of reaching the climate policy goals .

Types of biofuels

Today, all the transport fuels can be classified in fossil fuels. However, the process chains for all transport fuels are different because the various of primary sources are used for producing(see the figure below). The figure shows that there are various opportunities for the production of biofuels. And the features between two different biofuels are quite similar. For instance, biodiesel is similar to fossil diesel, and bioethanol is similar to pertol. This is a great advantage since the existing infrasture does not necessarily to be intensively change.

---

First-generation biofuels

PPO, biodiesel, ETBE and bioehthanol are the first-generation biofuels. They generally produced by the action of microorganisms and enzymes through the fermentation of any biological feedstock. Especially for bioethanol, the most commonly biofuel feedstock, offers the greatest short-term potentials of biofuels today since the conversion is widely developed and approved in practice . Although the first-generation biofuels are different in properties, technical requirements, economical aspects and potencial usages, they can contribute to gurantee a long-term sustainability.

Second-generation biofuels

Second-generation biofuels are derived from feedstocks, which are not traditionally used for human consumption. They include BTL fuels and ethanol from lingo-cellulose. These products are not yet commercial available since their conversion technologies are not improved enough as products of first-generation biofuels. However, second-generation biofuels are considered to be more environmental health and produce less GHGs than first generation biofuels.The reason is they can make use of the vast majority of feedstock in the process of production and avoid the waste inherent in the production of first generation biofuels. Second generation biofuels can not only help solve this waste problem, but also can supply a larger proportion of our fuel supply sustainably, affordably, and with greater environmental benefits.

---

The figure below focuses on the pathways of biofuel production. It shows that feedstocks sources can br divided into animal fats, oil crops, suguar plants, starychy plants, cellulosic biomass and wet biomass. During the different process, such as refining, extraction, hydrolysis and fenmentation etc., they can be transformed into liquid or gaseous biofuels.

Pathways of Different biofuels

Current biofuel promotion policies

A turning point for biofuels policies occurred in 2005–06, when several countries dramatically stepped up targets and mandates for biofuels to make a great promotion. The promotion of biofuels is attractive for the governments, especially for the one wants to take action to fight for global warming and diminish environmental pollutions, to set up a sustainable policy to future gobal energy requirements.

The result of recent policy activity is that biofuels blending mandates now exist at the national level. "In the United States, a renewable fuel standard was enacted in 2005 that requires fuel distributors to increase the annual volume of biofuels blended up to 7.5 billion gallons (28 billion liters) by 2012 (although this target was expected to be met anyway through tax incentives). The federal government also extended a 43 cents/gallon (12 cents/liter) biodiesel tax credit for blenders through 2008". It is clear that policy has played an important role in influencing on the promotion of biofuels.

Environmental benefits and problems

By the way of reducing GHGs and local pollution, biofuels can provide many benefits to the environment, for example, bioethanol, is water soluble, non-toxic and biodegradable. In addtion, bioethanol is not as flammable as petrol, which means that it can reduce the incidence of severe vehicle fires and it can be a safety transport energy in daily life. Compare to the carbon dioxide based fuels, it is an environmentally friendly option to use hydrocarbon-based fuels as a mainly energy.

But in Abdersib and Fergusson(2006) argue that "none of the fuels derived from biomass energy can be considered truly carbon-neutral when one bears in mind that stages of production, transportation and processing required non-renewable energy. Attention also need to be paid to crop types, especially since it is clear that some first-generation feedstocks are more applicable to biofuel production than others. " Besides, attention should also paid on the prodution, the application of fertilizers, pesticides and herbicides and the prodution of biofuels itself to guarantee they are not harmful to the environment in the long term.

Socio-economic benefits of biofuels

Generally, biofuels are expected to have a positive impacts in socio-economic, especially for local areas. Biofuel production is a new market for agriculture products and as a result, it offers the new income options for farmers. The increased feedstock production will have a significant contribution in the multi-functionally. Therefore, aguculture not only plays a role in food production, but also in energy provision in the future.

Case Study—Biofuels in China

Biofuels have become a broad debate in many countries' energy policies since it covers many aspects, such as energy security, food security, climate change mitigation, and international biofuel development. With 20 percent of world's population and 10 percent of its arable land, the center debate of biofuel production ins China is the conflict between food security and energy crops.

In January 2007, China’s State Forestry Administration (SFA) and the oil company PetroChina signed an agreement of developing diversity of potential energy crops, an oil-bearing plant, Jatropha. Jatropha curcas has considered as a high potential biodiesel feedstock in China since it grows on marginal land in Southwest China, and thus avoids the completion with food system. Southwest China, including Guizhou Province, Sichuan Province, and Yunnan Province, is the official target area for Jatropha production in China(see table below). Especially for Yunnan Province, it has significantly more land available for Jatropha production than neither Guizhou nor Sichuan Province. Therefore, Yunnan may be the p province capable of achieving the National Development and Reform Commission (NDRC)'s goal: to expand Jatropha plantations to 10 million mu in each Southwest province in China.

The Process of transferring Jatropha into biofuel

Estimate Current and Planned Jatropha Area in Southwest China by Province

Future studies

In the near term, biofuels investigation will continue under a US Department of Argiculture (USDA) and US Department of Energy (US DOE). These two parties support project will focused on : (1) life cycle analysis of biofuel liquid products and biofuels fired power plant feedstocks in comparison with coal and petroleum; (2) environmental biocomplexity analysis of socio--economic, technical, and environmental implications of biofuels use and (3) role of fundamental combustion developments for biofuel usage; (4) integrated enviromental and economic analysis of biofuels production; (5) technological innovations in farm biomass product yields and control of prodution and processing costs.