Cells make many chemicals that can be used as fuels, including ethanol, biodiesel, and even gasoline. Biological systems such as photosynthesis can also be adapted to create better solar panels
Many medicines that we used today were discovered in plants and other living organisms. Synthetic biologists are using techniques from genetic engineering to produce these medicines cheaply and to design new drugs for deadly diseases.
Genetically engineered foods can have a huge impact on hunger around the world. Agriculture is difficult in many places because of poor soils, not enough water, or harsh climates. Plants can be engineered to better resist such problems, as well as to need less fertilizer and fewer pesticides, or to provide more vitamins and minerals.
We use chemicals every day, in our daily life, and in manufacturing of other things. Biology can make these chemicals just like it can make fuels and medicines, and hopefully can do it cheaply, efficiently, and in an environmentally friendly way.
By engineering cells we learn more about them. We can prove our deep understanding of how a system works by building and redesigning it and we use synthetic biology to create tools that we can use for new biology experiments.