Viết tích hợp TOEFL

📖 Đoạn văn

The use of biofuels, such as ethanol derived from corn, has been championed as a sustainable alternative to fossil fuels. Proponents argue that biofuels reduce greenhouse gas emissions, enhance energy security, and stimulate rural economies. However, a closer examination reveals significant drawbacks that undermine these claims. Firstly, biofuel production requires vast amounts of agricultural land, which leads to deforestation and habitat loss. For instance, in Brazil, the expansion of sugarcane ethanol has encroached upon the Amazon rainforest, releasing stored carbon and reducing biodiversity. Secondly, the energy balance of biofuels is questionable. Producing ethanol consumes substantial fossil fuel inputs for farming, fertilizer production, and processing, often resulting in only marginal net energy gains. Some studies suggest that the energy return on investment for corn ethanol is barely positive, and when factoring in land-use changes, it may even be negative. Thirdly, biofuel crops compete with food crops for land and water, driving up food prices and exacerbating global hunger. As more corn is diverted to ethanol, the supply of corn for human consumption decreases, leading to higher costs for staple foods in developing countries. These environmental and social costs suggest that biofuels are not the panacea they are often portrayed to be.

🎧 Bài giảng

The reading paints a grim picture of biofuels, but its arguments are flawed and overlook key evidence. Regarding deforestation, the claim that biofuels cause land-use change ignores the fact that modern agricultural practices and yield improvements can reduce the need for additional land. For example, in the United States, corn yields per acre have increased dramatically over the past decades, allowing more ethanol production without expanding cropland. Moreover, many biofuel projects use marginal or degraded lands that are unsuitable for food crops, thereby minimizing competition with forests. On the energy balance issue, the reading relies on outdated studies that fail to account for technological advancements. Recent life-cycle analyses show that ethanol from cellulosic sources, such as switchgrass and agricultural residues, can achieve a positive net energy balance of up to 3:1, and even corn ethanol has improved significantly with better farming techniques and more efficient refineries. Finally, the food versus fuel debate is oversimplified. While biofuel production can influence food prices, the primary drivers of recent food price spikes include oil price volatility, speculation, and climate-related crop failures. In fact, biofuels can enhance food security by providing an additional income source for farmers, which enables them to invest in better irrigation and seeds, ultimately boosting food production. Therefore, the negative assertions in the reading do not hold up under scrutiny.