# Paper-Mill Wastes for Bioethanol Production in Relation to Circular Economy Concepts: A Review
## 2 Paper and Cardboard Manufacturing Process
### Manufacturing Process in Hadera Paper Mill, Israel: A Case Study  
Hadera Paper mill (\"Infinia\" group) is the largest paper and cardboard production and recycling factory in Israel. There has been a substantial increase in paper and cardboard recycling over previous years due to the operation of a new packaging facility that recycles cardboard and the improvement in cardboard collection, including from landfills. Paper waste is typically recycled multiple times (2.4 times in average), but through the recycling process, the fibers are shortened by mechanical erosion, resulting in large amounts of short fibers (up to 40% of input mass), termed recycled paper sludge (RPS). These short fibers are rich in cellulose but are currently disposed of in landfills, causing landfill filling, greenhouse gas emissions, and groundwater contamination. Table 3 shows the RPS material composition. The very high cellulose content of the RPS, and since RPS cannot be further used for paper recycling, makes it a very good feedstock for 2 nd generation ethanol production and other cellulose-based products like cellulose nanocrystals (CNC's) [5; 59], and eventually solve the costs for disposal of the paper waste sludge waste.  
The cardboard recycling facility in Hadera Paper and its wastes are illustrated in Figure 4. In the process, the raw material is made into a slurry in the pulper by mixing with water, where rejects are separated. This waste stream consists of low fiber content and a high content of plastics. Currently, this stream is landfilled but is evaluated as a future incrementation additive in power stations.  
The fiber slurry flows through a high and low consistency cleaner (HCC and LCC, respectively) and to a fiber sorter where rejects are transferred to the reject flow. The fractionator separates the fibers to long fibers (4.7% conc., >2.6 mm) and short fibers (2.2% conc., <2.6 mm). The long fiber undergoes fine cleaning, and the residues are collected on an extra-fine screen where the filtrate is the RPS. This RPS can also undergo mechanical de-watering processes such as Belt Filter Press or Screw compressors.  
Hadera Paper mill generates 31,000 tons of cellulose-rich RPS per year. Furthermore, given the recent advances in packaging material collection (\"Container law\") and the large quantity of paper and cardboard product in this waste, it is likely that more cardboard will be recycled in the future, and accordingly, more sludge will be generated. To date, this waste is used for dairy barns. Several publications have examined it as feedstock  
\begin{table}
\begin{tabular}{c c c} \hline
**Grade** & **Quality** & **Examples** \\ \hline
1 & Low & Corrugates board, unsold magazines, mixed magazine and newspaper, mixed-paper, and paperboard \\ \hline
2 & Medium & Newspaper, printed white shaving, sorted office paper, PE-coated paperboard, colored wood-free paper \\ \hline
3 & High & Wood-free binders, white wood-free paper, SBS paperboard, coated mechanical pulp paper \\ \hline
4 & Kraft & New shavings of corrugated board, used kraft paper \\ \hline
5 & Special & Liquid packaging paperboard, wet-strength wood free paper, and labels \\ \hline \end{tabular}
\end{table}
Table 2: Paper grades for recycling [58].  
\begin{table}
\begin{tabular}{c c} \hline Moisture (\%) & 40–45 \\ \hline Insoluble lignin (\%) & 8.22 \(\pm\) 0.22 \\ \hline Soluble lignin (\%) & 10.71 \(\pm\) 2.21 \\ \hline Crystalline cellulose (\%) & 75.30 \(\pm\) 20.20 \\ \hline Ash (\%) & 16.64 \(\pm\) 2.21 \\ \hline \end{tabular}
\end{table}
Table 3: RPS characteristics (dry basis), adapted from [60].  
for bioethanol production [61; 62; 63]. A recent publication showed the conversion of RPS to ethanol using the ozonation process as a pre-treatment stage, resulting in 94.42 \(\pm\) 0.013 g, ethanol/kg RPS [5], but with a higher yield and shorter hydrolysis time.