Biomass harvested at two energy plant growth phases for biogas production

The innovation of this research was a holistic approach to the problem of linking the biometric characteristics of six energy plants species and the distribution of moisture along the shoot' height and determination of linear models of particle sizes in relation to the moisture. The median biometric parameters values for growth phases I and II were as follows: shoot weight: 63 g and 65 g; stalk weight: 45.1 g and 43.8 g; plant length: 1273 mm and 2157 mm; shoot centre of gravity: 698 mm and 968 mm; slenderness ratio 147 and 215, respectively. For big bluestem and Spartina pectinata the largest values were for slenderness ratio and for phase II amounted to 403 and 410, respectively but most other parameters were the smallest values. Regarding the shoots' growth, the greatest influence was on the stalks by increasing their lengths more than their diameters. The highest difference in the plant length between harvest terms was observed for Spartina pectinata which increased from 793 mm to 2257 mm (by 185%). The lengths of the Jerusalem artichoke, miscanthus and big bluestem plants also significantly increased: from 1345 mm to 2920 mm (117%), 1214 mm to 2065 mm (70%) and 1064 mm to 1779 mm (67%), respectively. Positive correlation coefficient values between parameters (shoot weight, leaf weight, stalk weight and plant length) indicate that to characterize of plant shoots the shoot mass and plant slenderness could be used. The Rosin-Rammler function fit the chopped plan material size distribution data with an R2 = 0.909-0.991. All the biomass particle sizes belonged to the “very poorly sorted” category (2.00 mm ≤ σig ≤ 4.00 mm), and the particle size distributions were “fine skewed” (0.1 ≤ GSis ≤ 0.3) and “mesokurtic” (0.90 ≤ Kgs ≤ 1.11). For grasses relation of particle sizes vs. moisture for phase II (August for Spartina and big bluestem or October for miscanthus) was inverted to phase I (June) with slope coefficients −0.11 and 0.09, respectively. For leaf plants direction of the relation was preserved, wherein for phase II (all plants harvested in October) the growth dynamic was lower than for phase I and slope coefficients of the lines were 0.17 and 0.04, respectively. Moisture content of leafy plants was high, and its distribution along the shoots' heights was different than that for grasses. Varied values of particle size and weight of plant components, together with the change in moisture along the height of the plants, will impact the diversity of the dynamic loads of elements and working units of forage harvesters and can be useful to explain these results.