**3.1 Alternatives presentation and criteria definition**

Five low-tech alternatives are considered to treat the digestate obtained in a lowcost biogas digester implemented in a small farm in Colombia. As shown in **Figure 4**, all alternatives are implemented just after the biogas digester to posttreat the digestate. The five alternatives are given below:

• A1. Degassing tank alternative: It allows the recovery of the remaining diluted methane and stabilizes the organic matter producing more biogas.

**Figure 4.** *Five alternatives for digestate posttreatment, Adapted from [18].*

*Perspective Chapter: A Novel Method for Integrated Multicriteria… DOI: http://dx.doi.org/10.5772/intechopen.106589*


Also, combining alternatives in series (e.g., A1 + A2, A1 + A3, and A1 + A5) has been also considered for their complementary nature. Other combinations were not realistic in practice for small farms in rural areas.

These five alternatives are evaluated according to 10 criteria and 22 (sub)criteria (**Table 6**), selected after discussion with experts in the field and divided into three categories, namely technical, environmental, and socioeconomic [19]. The categories are defined as follows:

