Assessing the Carbon Footprint of Biochar from Willow Grown on Marginal Lands in Finland

Willow biochar can help to sequestrate carbon. However, biomasses should not be grown on arable lands, as it would increase competition with food production and lead to sustainability issues such as increased food prices and decreased food security. The purpose of this study is to calculate the carbon footprint (CF) of willow biochar in Finland and assess the greenhouse gas compensation potential of marginal lands if they are utilized for willow biochar production. The CF of willow biochar is inadequately assessed together with marginal lands in the literature. A cradle-to-grave Life Cycle Assessment (LCA) of willow biochar was conducted. The results were then applied to assess the total CF of marginal lands. It was found that the CF of willow biochar is −1875 kgCO2eq t−1 of dry biochar. Grown on marginal lands in Finland, willow biochar could compensate 7.7% of yearly agricultural greenhouse gas emissions. On buffer zones, willow biochar could also compensate some of the emissions depending on the zone size. The results of the study support current findings of biochar as a carbon negative product. The study also indicates that willow biochar produced in marginal lands can be used to compensate agricultural greenhouse gas emissions to some extent.

Reconfigurable Multifunctional Ambipolar Polymer Transistors with Improved Switching-off Capability Upon Non-Uniformly Distributed Compensation Potential

Ambipolar field-effect transistors allowing both holes and electrons transport can work in different states, which are attractive for simplifying the device manufactures and miniaturizing the integrated circuits. However, conventional ambipolar transistors intrinsically suffer from poor switching-off capability because the gate electrode is not able to simultaneously deplete holes and electrons across the entire transport channel. Here, we show that the switching-off capability of polymer ambipolar transistor is largely improved by up to 3 orders, through introducing non-uniformly distributed compensation potentials along the channel to synchronically tune the charge transport at different channel locations. Non-uniformly gate-stressed conjugated-polymer@insulator blend film induces non-uniformly trapped charges in the insulators, which consequently generates non-uniform compensation electrical field imposed in the conjugated-polymers. Both n-type and p-type operations with high mobility (2.2 and 0.8 cm2s-1V-1 respectively) and high on/off ratio (105) are obtained in the same device, and the device states are reversibly switchable, which provides a new strategy for three-level non-volatile memories and artificial synapses.