The most useful instrument for evaluation and handling of the current performance of all activities along a product chain is the assessment of Product Chain Quality.
The term „product chain quality” bases on a products life cycle (Fig 4) and on the assessments of product impacts on all components of the product chain inclusively unwanted side effects. Product chain quality summarizes the quality of segments certified by specific catalogues of criteria (Fig 4), e.g. GAPs for on-farm production or transport. The implementation procedure and the continual assessment of product chain quality are sometimes called “Total Quality Management” (e.g. www.sources.de).
The term “management” in several combinations indicates the act of directing people towards accomplishing a goal. Summing up segment evaluations product chain quality is considering several international commitments related to the performance of agricultural and trade/business practices.
The overall agreement is that agricultural products should try to be produced as sustainable as possible. That means that all practices must be profitable as well as “socially and culturally suitable" (FAO, 2004). Furthermore, agricultural practices and subsequent processes along the product chain have to meet the requirement of ecological sustainability. From the product chain quality assessment, therefore, the potential sustainability of a specific product chain can be deduced (see below). The commitments reflect the demands of several interest groups along the product chain including the producer with his employees, producer associations, individual retailers, retailer organizations, supply-chain driven systems, industry and – last not least - the consumers.
Their specific interests can be summarized in three main fields: societal demands, environmental demands and economic demands. Consequently, Meier (2002)- focussed on the on-farm production - asked for “social, environmental and economic compatibility” of production systems with “cultural compatibility as the central dimension of sustainable development”.
Societal demands (including e.g. social, sociological or cultural components), environmental demands (including aspects of e.g. soil, water, air, biodiversity or landscape protection) and economic demands (including e. g. healthy food for all and not restricted to those who can pay high prices) are in direct relationship to each other (Fig. 5). High prices influence societal demands, societal demands may lead to high prices, both may influence environmental demands and vice versa.
On that background, it is easy to demonstrate how those fields of demands influence sustainability (Fig 5): a circle within the triangle touching each side in one point differs in size when the length of the triangle sides change. The size of the circle serves as a measure for sustainability. In case of satisfaction of all demands an equilibrated, equilateral triangle develops with momentary optimal sustainability.
Basing on the requirements following from Agenda 21 the term “product chain quality”, can be described as a “combination of production and procesing factors resulting in a certain, temporary value of sustainability of the related product chain”. Because of the determination of sustainability by the sets of variables and factors, logically, aspiring higher sustainability is passing lack of equilibration in the triangle model between the fields of demands demonstrating the fields of necessary actions (Fig. 6). Here, we propose a very easy definition for sustainability in practice: sustainability should be understood as the length of the time period of unchanged use of factors with a certain level of product chain quality. This interpretation summarizes traditional characteristics of sustainability (e.g. the reaction norm to stress) with stability of productivity, trade and consumer aspects.