According to the biological sciences, an ecosystem is a community of living organisms functioning together with the non-living component. Concurrently, industrial systems are linked to one another through flows of energy, material and process. This might be defined and explained as an Industrial Ecology system (Garner & Keoleian,1995). As occur with biological studies, this field can be analysed in different levels of aggregation such as flows of energy and materials processes in the industrial system, understanding their nodes and mechanisms. With this knowledge, it is possible to predict and improve the industrial systems through their interactions. Therefore, this approach requires the analysis of several levels of aggregation in the system to develop new initiatives and activities.
A resource efficient way which led normally unrelated industrial organizations to establish a close working agreement is called industrial symbiosis (Jensen et al. 2011a). Industrial symbiosis from one side increases profits, sales, jobs, utilisation of assets, innovation and knowledge transfer and form the other side it can reduce CO2 emissions, costs, pollution, transport, risk and hazardous waste (Laybourn & Morrissey, 2009).
Closed loops material systems can improve materials sustainability, additionally, environmental aspect of these activities suggests that closing material circulation loops are economically and eco-friendly attractive (Frosch et al, 1997). In fact, using industrial symbiosis as a concept will lead the industries to think more in this closed loop material system in order to benefit economically and environmentally.
Industrial Ecology (IE) is an attempt to develop a new network into an industrial system. That means, creating interactions and connections for an industrial environment, achieving reduce of materials and energy, improving the production and waste relationships between producers, consumers and other nodes in the systems. Keeping the natural ecology studies perspective, (IE) suggests that the waste from one firm it might be a potential raw material for another. Furthermore, offer the idea to study the industrial system through observation, data collection and analyses in different levels of aggregation. IE should be considered as an approach to examining industrial systems issues creating closed loops materials, reducing waste flows and saving energy (Sagar & Frosch, 1997).
The linear system of production, shown in Figure 1, consumes more natural resources and there will be more waste for disposal which can be changed to a more economical and eco-friendly way of a circular system in which most of the waste products can be used as a resource for different purposes.
Industrial symbiosis, as part of the emerging field of industrial ecology, (see figure 2, pay attention to mass flow analyse (MFA) and energy flows through local and regional economies. As opposed to traditional industries which, involve a collective approach to compete for material energy and by-products, industrial symbiosis offers collaboration and synergies between firms in the same geographical area. Industrial ecology allows focus at environmental design, pollution prevention and green accounting while industrial symbiosis occurs in the eco-industrial parks with product life-cycles because it includes the exchange of material and energy (Chertow, 2000).
Industrial symbiosis can offer by-product reuse by exchange of material between firms to be used as substitutes products or raw materials, infrastructure sharing, providing services and meeting common needs across firms. Many motivations exist for pursuing industrial symbiosis such as reduce cost or increase revenues. In some levels, the firms can Increase the availability of critical resources such as particular raw material or firms pursue symbiosis in response to regulatory requirements to increase efficiency or resources, reduce emissions or eliminate waste (Chertow, 2007).
Following ecologists and natural sciences field, we can conclude that ecosystems with a high rate of biological diversity are generally more stable and productive (Sagar & Frosch, 1997). This explains that it is not necessary to create an industrial symbiosis just for one specific material in the industrial system as the happens with ecosystems. Furthermore, identify a representative species in an industrial symbiosis protecting their interaction with other firms as also happens in the natural system. This can be, for example, the energy plant which, contributes mainly to set up the industrial ecosystem. This can be done by policy protection by taxes reduction on the heat supply connection between firms in different level aggregations. Therefore, policy implications take an important role to implement industrial ecosystem in the future.
In addition, taking into account the idea to be focused on a stable and production industrial ecosystem, the strategy might be to promote diversity between firms with the policy implications of materials and energy, metals and heat supply connection in many cases.