The Nexus between Energy, Food, Land Use, and Water
Application of a Multi-Scale Integrated Approach

How it works

  • The Nexus Assessment Project was commissioned by the Energy Team of the Climate, Energy and Tenure Division (NRC) of the UN Food and Agriculture Organisation (FAO)

    and sponsored by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ).

In practical terms, the proposed nexus assessment involves the following six steps:

STEP 1: Definition of the socio-economic system as a set of functional compartments guaranteeing survival, reproduction and adaptability

This first step involves the definition of the nested hierarchical structure of functional compartments of society. We first define the overall system (the boundaries), at level n, and then define within this “whole” a set of lower-level compartments at level (n-1) (e.g., household sector, paid work sector) on the basis of the functions expressed in society (e.g., reproducing human labour, generation of income).  These lower-level compartments can then be further subdivided (level n-2, n-3, etc.) depending on the aim of the study. The definition of compartments must provide closure at all levels (the sum of the size of the parts must equal the size of the total) and be mutually exclusive (no double counting). Moreover, it must be practical for data collection: the data required to define both the size and the characteristics of individual compartments must be amenable to subdivisions practiced in national statistics. The nested hierarchical structure used in our case studies is illustrated in Figure 1.

The socio-economic sectors can be aggregated into two macro-compartments expressing emergent properties observable only at a larger scale (Figure 1): (1) a hypercyclic part that generates the required flows (food, energy, mineral, water), technology and infrastructures for its own use as well as for use by the rest of society; and (2) a dissipative part that consumes the surplus generated by the hypercyclic part and allows for adaptability and reproduction of the fund elements. This distinction allows us to analyze the viability of the dynamic equilibrium of the various flows (energy, food, water) in the impredicative loop analysis (see step 5).

STEP 2: Quantitative definition of the profile of investment of fund elements over the functional compartments of the system

This step involves the selection of relevant fund elements and their quantification across the various functional compartments of the system. In our case studies, we select three fund elements, human activity, power capacity, and managed land, and assess their allocation over the various socio-economic sectors of society. This step typically results in the generation of dendrograms in which the total amount of fund element assigned to the whole society (on a year basis) is repeatedly split up as we move further down its nested hierarchical structure. This procedure is illustrated in Figure 2 for the fund element human activity (left side of graph) and the flow element energy (right side of graph). Clearly the depth of the dendrogram depends on the goal of the study and the availability of data for the fund (and flow) element in question.

STEP 3:  Quantitative definition of the flows required for expressing the functions

This step involves the definition and quantification of the various flows (food, energy, water, money) used by the selected fund elements associated with the various functional compartments at different levels. For this purpose, MuSIASEM makes use of a series of grammars that describe the internal loops associated with the supply and consumption of the various flows.  The grammars developed for energy, food, and water and used in our case studies are illustrated in Figs. 3, 4, and 5, respectively. Four pieces of information are essential to the construction of these grammars:

  1. Gross supply/requirement: the overall flow that must be produced or made available through imports;
  2. Net supply/requirement for “end-uses”: the net flow required by the various functional compartments to guarantee final uses.  The characteristics of these “end uses” are defined by the grammars both in quantity and quality;
  3. Losses: the fraction of the flow that does not make it to final consumption because it is lost in the network;
  4. Internal autocatalytic investment: the share of the flow that must be invested in its own production. This specifically concerns the metabolic pattern of energy and food, where a fraction of the net supply is consumed internally by the compartment producing the flow. Indeed, energy carriers are used in the energy sector to produce energy carriers, and food products (seeds, eggs and crops used as feed) are used in the agricultural sector to produce food products. This internal investment in an autocatalytic loop is therefore not “available” for consumption by the other compartments.

STEP 4: The multi-level, multi-dimensional matrix describing the metabolic pattern across hierarchical levels and dimensions of analysis

Having defined and quantified the funds and flows, MuSIASEM makes use of a multi-level, multi-dimensional matrix of flow and fund elements to combine and represent the various descriptions given by the dendrograms (step 2) and the grammars (step 3). In this way, we obtain an integrated characterization combining non-equivalent quantitative descriptions of the metabolic pattern across different hierarchical levels/scales (e.g., the whole, its compartments, and their subsectors) and different dimensions (e.g., demographic, economic, biophysical dimensions) of analysis. Indeed, confronting the distribution profiles of the flow elements (energy, food, water, money) to those of the fund elements (human activity, power capacity, managed land) across the different functional compartments (HH, SG, BM, AG and EM) we obtain a set of flow/fund ratios (see example in the centre of Fig. 2) that effectively describes (diagnoses) the characteristics of the metabolic pattern of society.

STEP 5: Checking the viability and desirability domain for the metabolic pattern (definition of the internal constraints of sustainability)

A metabolic pattern is viable if, given the structural constraints (supply of production factors/fund elements), it is capable of generating an adequate internal supply of the various flows it consumes (food, energy, goods, infrastructures, services). Viability is checked by cross-verifying the stability of the dynamic budgets of the individual flows (food, energy, water, money). For example, the total flow of food consumed by society must be provided by the agricultural sector or imported.  This food supply has to be secured with only a limited share of the production factors (human labour, power capacity, managed land) employed in either producing or importing food (= producing and selling other products of an equivalent economic value).  The same applies to energy, water, and other flows.  As the sum of the production factors (human labour, managed land, power capacity) MUST equal society’s total endowment, we obtain an integrated set of forced relations across the dynamic budgets. This is what we call the Sudoku effect.

At the macro level of analysis, the desirability of the metabolic pattern refers to the internal pressure on a socioeconomic system to allocate a relatively large share of the fund elements (human activity, power capacity) and consumed flows (energy, food and water) to the household sector, the service & government sector and the transportation sector (together the so-called “dissipative compartment”), so as to guarantee a relatively high standard of living. It concerns the question whether society can afford a large so-called “societal overhead” on human labour in the primary and secondary sectors (how large is the surplus generated by the hypercyclic compartment?). At the local level, the desirability check concerns a comparison of the resulting metabolic pattern at the level of end-uses (e.g., net energy supply per hour of labour in biofuel production) to reference values of flow/fund ratios (expected features of the functions expressed) characteristic of given types of socioeconomic systems.

STEP 6: Checking the feasibility of the metabolic pattern in terms of resource requirement (supply side) and environmental loading (sink side) - definition of external constraints to sustainability

By looking at the aggregate gross requirement of biophysical flows and the corresponding flow of wastes we can assess the environmental loading of a given metabolic pattern: that is, the overall requirement of natural resources on the supply side (either directly used or embodied in imports) and the sink capacity. It is important to realize that the gross requirement (and the resulting flow of wastes) describes the interaction of society with its natural environment and hence does not equal the net requirement of biophysical flows consumed by the various compartments within society.  For example, in the assessment of the resource requirement and sink capacity for agriculture we not only consider the food effectively consumed by the population (the net requirement), but also the feed crops involved in animal products (the internal autocatalytic loop in the agricultural sector) and the post-harvest losses in the food system. The same applies to the resource requirement (primary energy sources) and sink capacity (CO2 emission) for the energy sector: we not only include the final consumption of energy carriers (electricity, fuels and heat) inside society (net requirement), but also (i) the fossil energy consumed in the double conversion of thermal energy into electricity; (ii) the losses in conversion and distribution, and (iii) the effect of changes in land uses on atmospheric CO2. The quantitative analysis of the interaction of society with its context (the embedding ecosystems) is articulated in spatial terms across scales, using GIS data.  Indeed, levels of environmental loading, defined as the difference between the flow densities of natural land cover and those of managed land uses, have to be assessed simultaneously at different hierarchical levels and scales (e.g., soil, crop field, watershed, national scale, global scale). The scaling of this quantitative information can only be handled by employing GIS.

Further reading

M. Giampietro, K. Mayumi and A.H. Sorman (2012). The Metabolic Pattern of Societies - Where economists fall short, Routledge.