## 2 Materials and Methods  
### Search Strategy and Selection Process  
This study conducts a review of the available literature on energy use data in greenhouse cultivation within the EU. Our search strategy used a key word search of Google Scholar and SCOPUS and the selection criteria for a paper's inclusion in this study were:  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**County** & **2005** & **2007** & **2010** & **2013** \\ \hline Belgium & 2140 & 2120 & 2060 & 1800 \\ Bulgaria & 900 & 1140 & 1090 & 1080 \\ Czechia & 180 & 190 & 0 & 0 \\ Denmark & 450 & 470 & 460 & 400 \\ Germany (until 1990 former territory of the FRG) & 3370 & 3430 & 3170 & 3110 \\ Estonia & 60 & 60 & 40 & 40 \\ Ireland & 60 & 30 & 60 & 180 \\ Greece & 4670 & 5340 & 4290 & 4730 \\ Spain & 52,170 & 52,720 & 45,700 & 45,200 \\ France & 9620 & 9790 & : & 11,190 \\ Croatia & : & 250 & 410 & 500 \\ Italy & 28,640 & 26,500 & 39,100 & 38,910 \\ Cyprus & 420 & 430 & 450 & 420 \\ Latvia & 110 & 80 & 50 & 40 \\ Lithuania & 1010 & 450 & 310 & 330 \\ Luxembourg & 0 & 10 & 0 & 0 \\ Hungary & 1910 & 1760 & 1960 & 2260 \\ Malta & 70 & 70 & 80 & 100 \\ Netherlands & 10,540 & 10,370 & 9820 & 9330 \\ Austria & 290 & 580 & 620 & 720 \\ Poland & 7170 & 7560 & 6630 & 8080 \\ Portugal & 2310 & 2220 & 2360 & 2490 \\ Romania & 2790 & 3250 & 3020 & 3300 \\ Slovenia & 170 & 180 & 170 & 160 \\ Slovakia & 250 & 190 & 150 & 100 \\ Finland & 450 & 440 & 420 & 400 \\ Sweden & 420 & 180 & 200 & 260 \\ \hline Total & 130,170 & 129,810 & 122,620 & 135,130 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Area of vegetables, flowers, and permanent crops under glass EU-27 (ha) [19].  
the presentation of energy use data based on either LCA methodologies or surveys, whether they were peer-reviewed, and whether they were published by well-respected journals or institutions. In some cases, data from reports were used if they were extensively cited in existing literature. The methodology, relevancy and accuracy of each study was evaluated for relevancy and accuracy and the wider project partners of the AgroFossilFree consortium [20]. Overall, 24 relevant published articles and reports were located in the first part of the search process. Of these, after the evaluation process, 13 were discarded due to methodological issues. From the remaining 11 studies, data were extracted and used for this review.  
For this study, energy use was defined according to operations and included direct energy uses--on-farm operations, heating and cooling, lighting, irrigation--and indirect energy uses--energy embedded in the production of fertilizers and pesticides. Energy assigned to the production and establishment of agricultural infrastructure, such as agricultural machinery and greenhouse constructions, was not included due to difficulties associated with accurately measuring and reporting on this and most studies do not provide data on this. This is mainly because agricultural infrastructure is often in use for multiple decades and undergoes a variety of production processes which makes it difficult to accurately assign a yearly energy use values to these components. These energy input data for greenhouse production were extracted from each study and compiled and compared to existing studies for verification.  
The research questions that guided our research included: what are the specific energy sources in greenhouse production processes? What are the energy needs for different types (high intensive to low intensive) greenhouses? How do the energy needs of greenhouses vary depending on geography and climate across the EU?