Kinetic and hydrogen production analysis in the sequential valorization of a Populus clone by cold alkaline extraction and pyrolysis.

This work employed a two-step biorefining process, consisting of a hemicellulose-rich liquor production through ultrasound-assisted cold alkaline extraction (CAE), followed by thermochemical treatment of the resultant solid phase. The post-CAE solid phase's pyrolytic potential was assessed by application of thermogravimetric analysis (TGA) and Friedman's isoconversional method, and also from hydrogen production. The solid phases remaining after the CAE treatment were more reactive than the untreated raw material. Notably, the alkali concentration employed in the first step was the individual variable most pronounced influence on their activation energy (Ea). Thus, at a degree of conversion α = 0.50, Ea ranged from 109.7 to 254.3 kJ/mol for the solid phases, compared to 177 kJ/mol for the raw material; this value decreased with rising glucan content. At maximal degradation, the post-CAE solid phases produced up to 15.57% v/v more hydrogen than did the untreated raw material.

Optimizing composting parameters for nitrogen conservation in composting.

A central composite experimental design was used to investigate the influence of environmental composting parameters (moisture, aeration, particle size and time) for legume trimming residues, used on soil restoration, on the properties of products obtained (organic matter, Kjeldahl-N, C/N ratio and nitrogen losses (N-losses)) in order to determine the best composting conditions. A second-order polynomial model consisting of four independent process variables was found to accurately describe (the differences between the experimental values and those estimated by using the equations never exceeded 10% of the former) the composting process. Results of the experiment showed that compost with acceptably chemical properties (OM, 85%; Kjeldahl-N, 3.2%), high degradation and minimum N-losses entails operating at high operation time (78 days), low particle size (1cm), medium moisture content (40%) and medium to low aeration level (0.2-0.4 l air/min kg).

Leucaena species valoration for biomass and paper production in 1 and 2 year harvest.

In order to identify faster-growing non-woody species usable for biomass and paper production, four Leucaena species (L.diversifolia, L. colinsii, L. salvadorensis and three varieties of L. leucocephala) were tested. All the Leucaena species showed a good soil and climatic adaptation to Spain Southwest except for L. salvadorensis. Studied Leucaena species showed biomass productivity ranges from 67.14 to 9.44 t ha(-1) (o.d.b.) and 43.6 to 11.4 t ha(-1) under Mediterranean conditions for the first and second year sprouts, respectively. The quantity of solubles and extractives shows similar values when compared with wood materials. Relatively lower lignin content in Leucaena (from 15.7% to 21.4%) species has been found with respect to other vegetal species. The alpha-cellulose contents (39.4-45.3%) are in the range of the normal values expected for the other non-wood raw materials. The study confirms the feasibility of organocell yield pulping process to Leucaena species. Organocell process provides an efficient delignification (kappa number 12.4 and pulp yield 42.2%) for L. leucocephala and suitably physical characteristics of paper sheet (tensile index 20.3 kNm/kg for L. diversifolia).

The use of Tagasaste (Chamaecytisus proliferus) from different origins for biomass and paper production.

In order to identify faster-growing non-woody species usable for biomass and paper production, four Tagasastes (Chamaecytisus proliferus) from different origins are tested. All the Tagasaste species (T. Huelva, T. Australia, T. New Zealand and T. La Palma island) show a good soil and climatic adaptation to Southwest Spain. The studied Tagasaste provenances shows biomass productivity ranges from 1.0 t ha(-1)yr(-1) to 3.4 th a(-1)yr(-1) (o.d.b.) and 25.3 t ha(-1)yr(-1) to 49.4 t ha(-1)yr(-1) under Mediterranean conditions for first and second year sprouts, respectively. The quantity of solubles and extractives shows similar values when compared with wood materials. A relatively lower lignin content in Tagasaste (from 13.7% to 17.1%) species has been found with respect to other vegetal species. The alpha-celullose contents (43.6-45.3%) were in the range of the normal values expected for the other non-wood raw materials. The study confirms the feasibility of the organocell yield pulping process to Tagasaste provenances. Organocell processes provide an efficient delignification (kappa index from 7.2 to 10.9 and pulp yield from 43.6% to 54.1%). The best results are obtained for the physical properties of paper sheets for Tagasaste from Australia in the second year, with values of tensile index of 16.0 kNm/kg, burst index of 1.12 MPa m2/kg and tear index of 0.55 Nm2/kg.

Soda-anthraquinone, kraft and organosolv pulping of holm oak trimmings.

The operating conditions for an organosolv (ethyleneglycol) and two alkaline (soda-anthraquinone and kraft) processes for obtaining cellulose pulp and paper from holm oak (Quercus ilex) wood trimmings were optimized. A range of variation for each process variable (viz. temperature, cooking time and soda or ethyleneglycol concentration) was established and a central composite experimental design involving three independent variables at three different variation levels was applied. The results obtained with the three cooking processes used were compared and those provided by the kraft process were found to be the best. Thus, the tensile index values it provided (5.9-16.3 N m/g) were 23.7% and 41.5% better than those obtained with the soda-AQ and ethyleneglycol processes, respectively. Also, the kraft process provided the best burst index, brightness and kappa number values. Based on the optimum working ranges, the temperature and cooking time were the variables resulting in the most and least marked changes, respectively, in pulp properties.