Anaerobic digestate has been commonly used for the cultivation of vegetable seedlings and as one of the measures for improving the peat-substrate. Studies have shown the influence on aromatic plants, and leafy vegetables, but no further research about the effect on greenhouse vegetables. The main objective was to investigate the effect of the additional insertion of different rates of solid grain waste digestate in the peat-substrate on tomato seedling quality. The research was carried out in a greenhouse covered with double polymeric film at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Two factors were investigated: seedlings establishment method (transplanted and direct sowed in the pod seedlings) and different substrates: control (peat), peat +10% digestate, peat+20% digestate with 3 repetitions by using a completely randomized design. The biometrics and photosynthetic parameters of the seedling were evaluated. The results showed that 10 % of solid grain waste digestate application with transplanted seedlings had a significant effect on plant height, leaf number, leaf area, and all plant fresh mass of tomato seedlings compared with the control variant. Photosynthetic parameters such as photosynthetic rate and transpiration rate of transplanted seedlings with 10 % digestate application were also higher. Transplanted seedlings with a 20 % rate of solid grain waste digestate showed the increase leaf chlorophyll index and nitrogen balance, but not in biometrics of the seedlings, and their photosynthetic parameters showed no significant difference between other variants. The use of different solid grain digestate rates can increase tomato seedling biometrics and photosynthetic parameters. The research showed that all transplanted variants of tomato seedlings have better biometrics and photosynthetic parameters comparing with direct sowed in the pod seedlings.

The increasing demand for animal products has triggered the scale-up from traditional household breeding to large-scale livestock farms with concentrated animal feeding operations (CAFOs), resulting in the production of a significant volume of livestock wastewater containing a large amount of nutrients and antibiotics. The improper management of this agricultural wastewater before discharge to surrounding freshwater ecosystems can easily deteriorate the natural environment. Here, we used the dairy livestock wastewater to cultivate the microalgae for nutrient recovery along with the surface water protection. We successfully cultivated two microalgae species of Chlamydomona reinhardtii and Chlorella protothecoides by using 100% dairy livestock wastewater [pH: 8.76 ± 0.04, conductivity: 6.57 ± 0.07 mS/cm, total organic carbon (TOC): 153 ± 5.54 mg/L, total nitrogen (TN): 298 ± 12.1 mg/L, PO₄^3--P: 6.42 ± 0.79 mg/L]. We further investigated the microalgae growth and nutrient removal under 1000, 3000, 5000, and 7000 LUX with light on for 12 hours per day. OD₆₈₀ showed a similar tendency between 5000 LUX and 7000 LUX, which were higher than those under 3000 LUX and 1000 LUX. OD₆₈₀ under the same simulated sunlight intensity was similar between the two microalgae species. pH was significantly increased after the microalgae cultivation, without obvious variations among different treatments (i.e., light intensity and microalgae species). During the microalgae cultivation, we observed the consumption of 12-28% of TOC mass, 88-95% of TN mass, and 58-74% of PO₄^3-–P mass. Specifically, more than 99% of NH₄⁺–N mass was used for microalgae growth. We observed a significant decrease of SUVA₂₅₄, indicating the aromaticity reduction of the wastewater after the microalgae cultivation. Total fatty acid content testing indicated C16:0, C18:1, C18:2 as the major fatty acids of C.reinhardtii and C. protothecoides, and their total fatty acid contents reached up to 13% and 17% by dry weight respectively. Our study concluded that the dairy livestock wastewater was successfully used to cultivate two microalgae species of Chlamydomona reinhardtii and Chlorella protothecoides for nutrient recovery as well as the potential biofuel production.