the company's management or the idea that an environmentally friendly management guidelines will give a positive image of the company and its goods. In other words, these thoughts are based on economic and ethical reasons. The Kyoto Protocol can be an example: It was intended to solve global problems of climate change and global warming; however, some companies had already put reducing emissions and getting better energy efficiency into practice, which is helpful to create a positive public image. Nature An environmental enterprise is an environmentally friendly/compatible business. Specifically, an environmental enterprise is a business that produces value in the same manner which an ecosystem does, neither producing waste nor consuming unsustainable resources. The concept is rooted in the well-enumerated theories of natural capital, the eco-economy and cradle to cradle design. The flow process shows the loop between enterprise and natural capital. Evidently, nature is the spring of wealth and the only thing that could and should be done is to promote the economy efficiency in the inner cycle.[6] In another word, strengthening the utilization ratio of raw materials to increase output, and meanwhile, enhancing the technology to reduce input of sources and waste products. To accomplish sustainability is, in this case, to make the economy functioning better. External cost In economics, an externality is the cost or benefit that affects a party who did not choose to incur that cost or benefit. The cost of the environment is usually termed as the external cost of an enterprise. Air pollution from burning fossil fuels causes damages to crops, (historic) buildings and public health. "Social cost − private cost = External cost". The ideal situation of environmental enterprise is to cut the negative external cost. Social cost Social cost in economics may be distinguished from "private cost". Economic theorists model individual decision-making as measurement of costs and benefits. Social cost is also considered to be the private cost plus externalities. For example, the manufacturing cost of a car (i.e., the costs of buying inputs, land tax rates for the car plant, overhead costs of running the plant and labor costs) reflects the private cost for the manufacturer (in some ways, normal profit can also be seen as a cost of production; see, e.g., Ison and Wall, 2007, p. 181). The polluted waters or polluted air also created as part of the process of producing the car is an external cost borne