Before going into agriculture, and the available figures for it, I will briefly summarize how evaluate keeping resource loops closed. Fot this a calculation method has been developed, called MAXergy, with Embodied Land as a measuring unit.
To close resource cycles, or to keep them closed, a number of conditions must be met:
– the use of sources should not go exceed the speed by which nature can restore these.
– If sources will not be restored within human generation’s time, the use should be limited, and possible mankind itself should take care of restoring .
– The energy that is put into the use of resources must be limited, and should also fit within a closed loop approach.
In practical terms, it means that all resource use can be expressed in energy: energy to grow or yield raw materials, and to convert these into usable products. Next, energy to use the end products, (operational energy), and lastly energy to restore the stocks (By means of renewable energy, not fossil energy of course. Possibly labor, as a form of sustainable energy)
Summarized as EE + CE + OE: being Embodied energy, Circular energy and Operational energy. Incidentally, including 2nd and 3rd order effects of materials, such as the impact of the use of materials for vehicles and factories for example. In fact this is the formula for a closed cycle approach, (also sometimes called “closing cycles calculation tool”).
When using energy sources from within the system (-earth), those stocks will also have to be restored. Since energy use is always accompanied by energy loss, (better exergy loss), there is actually only one option , which is to use the only source from outside the system: the sun (radiation) and secondary secondary forms such as wind or water power. ( requiring materials to convert the energy, which should be included into the evaluation)
The (solar) energy to maintain and utilize these cycles can be expressed in land use. Directly as for the growth of raw materials, or indirectly, to convert solar energy into desired forms, such as via solar panels in electricity (land for the arrangement of the panels, but also land needed to compensate for the materials used, the circular energy) . Land is therefore the common denominator in the closing of cycles. So EE +CE +OE are expressed in “Embodied Land”.
Labor can also be converted into land use. See our publications from 2010 and 2011 [1, 2] and the applications of the calculations in a comparison of materials in the IMDEP project 
In 2017, Michiel Ritzen obtained his doctorate at the Eindhoven University of Technology , using the MAXergy approach for a part of his work.  Recently another PhD, Meino Smit in Wageningen University, used these principles to a certain extent in his calculations for Dutch agriculture, while he himself was already on track to include secondary and tertiary effects.  On pages 46-47 he explains the approach, ( as a summary of his interview with me), about Embodied land and calculating ‘system-neutrality’ * . He provides a wealth of data on agriculture. , and his research includes 3 indicators for agriculture: land use, labor input and energy use, in a comparison of the situation in 1950 and 2015. see Table 1.
He shows that agriculture only flourishes because it makes an enormous claim on sources outside that agriculture, extra land and fossil energy. The Energy invested in agriculture is much higher than what comes out of food energy (per hectare of direct and indirect land). The only sustainable solution, according to his study, is agriculture that reinstates labor, uses (existing) greenhouses only unheated, and abolishes cattle farming. Then agriculture comes within sustainable limits, and is then just enough to feed the Dutch population.
Smit also gives totals for NL, but I limit myself here to the normalized values per hectare.
|Input Energy||165 GJ/ha-year||23 GJ/ha-year|
|Input Land||2,,7 ha/ha-year||1,16 ha/ha-year|
|Input labor||0,16 lye||0,26 lye||lye: labor years equivalent|
|Output energy||26 GJ/ha||23 GJ/ha|
In 1950, there was as much energy produced as was spent, but then in the usable form: food. Somewhat more land was needed than the actual harvested hectare, and a quarter of an annual labor year had to be invested. In 2015, these relationships are different: the input of energy is now a factor 6 higher than the output! In addition, it requires substantial extra land more then the actual grown hectare. Labor input has fallen slightly, of course. (But that is also disadvantageous, because that working time now is invested for other impacting activities: either extra work somewhere else, or longer holidays and flying for example, compared to 1950) That is obviously not sustainable, with a EROI of 6:1. Agriculture is in fact a big net energy destroyer.
However, MAXergy with Embodied Land goes one step further, and brings those three data: land, labor and energy into 1 number, without weighting factors, recalculated for Land use only. After all, energy use is also land-related: via solar energy; and even the fossils are fossilized biomass, originating from land (or seabed), While labor ‘lives’ from land. In the end, land is our real capital.
To see if we can make the complete closed cycle calculation, with the help of Maxergy and the Embodied Land indicator.
|Voor 1 ha voedsel gaat erin:||or||Is EL|
And its possible: With energy expressed in the required m2 PV, plus the land required to restore resources , again in (Circular) energy m2’s . Land remains land, and labor in terms of the land needed to provide the food (energy) , to keep the laborer going.
The total impact, expressed in Embodied Land, is 7.7 hectares, required for the yield of 1 hectare! Back in 1950 the total was only 1.9 hectares. (and of course that was 1 or less (ex-solar input) before the industrial revolution, see Vaclav Smil in his latest book about this) 
Incidentally, that is still not the full cycle calculation as outlined at the beginning. There is indeed the secondary and tertiary direct land use (for factories etc) and the embodied energy of that secondary and tertiary use (for the construction of tractors etc) but not yet the last step, the circular energy. CE: the energy needed to restore the cycle for all materials used (from factories, tractors etc). And that is, according to earlier calculations, certainly where metals are concerned, the biggest bite: bringing the metals of tractors, factories and transport back into a closed loop, requires immense energy. There is a way to partially limit this CE, as Ritzen introduced / showed in his calculations: recycling could reduce that impact significantly, but then the material must remain in circulation forever, in order to make redundancy unnecessary. But even then there is a remaining impact of that Circular energy, since 100% recycling is impossible. But even , a possible reduced, CE part is not included in this calculation. Nevertheless, without that part, the the outcome is already disastrous enough.
By the way: for other sector similar outcomes are expected, it happens that for agriculture now the data have been collected and calculated. More of these fundamental research approaches are needed!
1Assumed is energy is from renewable resources, PV, while every m2 of PV requires another 130 m2 to restore material stocks ( to generate Circular Energy for that) .
2Its assumed 3000 m2 pp required for an affluent diet, in open land agriculture
3This is still without full CE, see txt
Agriculture therefore destroys more than it produces! Whether from mass viewing, energy, land use, or integral with Embodied land, it is an untenable situation.
And even the 40% higher photosynthesis recently announced in at study, and yield, will not help. Maybe in the food supply, but not in the prevention of system exhaustion. Moreover, the 40% higher photosynthesis can only have an effect if enough raw materials are present to support the extra 40% biomass growth, such as phosphorus and nitrogen, for example. Let that be a limiting factor. And at the same time, through artificial fertilizer, the most impact rich factor. Add that to the fact that the technique does not work for all crops, I still have my doubts if we really can make progress in food yield. (and then still within the current system).
* ‘System-neutral’: I distinguish 3 levels in our climate and environmental problems: energy-neutral: we switch completely to renewable energy sources: but that is not climate or CO2 neutral: for that we have to include the materials required, especially the energy that it is invested should be ‘energy neutral, or 0-CO2 , as well. In that case climate neutral could be the case. However climate is only one consequence of our consumptive behavior. Its not the cause. In the end we exhaust the raw materials from our closed (earth) system, with many other consequential effects. In order to correct that too, we have to go to a System neutral approach: including to restore or maintain the raw material stocks. MAXergy was developed for this purpose by introducing Circular Energy and measuring it in Embodied Land.
 Rovers R., 2013, The Embodied Land indicator , Background and substantiation, RiBuilT report,
 Circular Energy, the missing link. R.Rovers, Paper Exergy, Life Cycle Analyses and Sustainability Conference, ELCAS, Greece 2017
 Houben, Jos, (2016) , IMDEP – Balken uit Hout-Bamboe-Staal-Aluminium – v1.0, plus the annexes: IMDEP – Balken uit Hout-Bamboe-Staal-Aluminium – v1.0 – Annex X, and the excell with data: MAXergy – Beams out of Wood-Bamboo-Steel-Aluminium – v1.0 Available via http://www.maxergy.org/downloads/
 Carrying capacity based environmental impact assessment of Building Integrated
Photovoltaics, chapter 8 , PhD thesis Michiel Ritzen: “Environmental impact assessment of Building Integrated Photovoltaics” , 2017, https://pure.tue.nl/ws/files/77700210/20171012_Ritzen.pdf