The core idea behind my diagram is that showing how to make full use of waste and get benefit from them. Biogas exactly illustrates the interaction relationship between human activities and the environment. Before people introduce biogas, they use wood as fuel, and that actually cause a series negative influence on both human and environment. By using biogas technology, cow dung, food, and other organic matter breakdown and produce a mixture of gases that can be used as fuel. Moreover, this can be considered as a Positive Feedback loop. Waste produce gas and fertilizer, and gain more farmer and animal product, then more waste will use for biogas production. Unlike the dam totally relies on the nature, biogas only takes advantage of nature. In other words, the first condition is uncontrollable, and the second condition can be controlled. Those are depended on sustainability. The dam influenced nature system dramatically, but the biogas didn’t.Comparing to the Figure 1.5, the same thing is that both of the diagram shows the relationship between biogas, society and ecosystem. However, the different thing is the form of diagram. Figure 1.5 list social system’s benefits on the left and ecosystem’s benefit on the right.  However, my diagram shows biogas as the center of two systems, and connect to the core I list what will happen. According to these two examples, we can learn that the form of the diagram depends on  your concerns.